Like Greg Says (He worked with my Dad at the WP in Stockton, Dad was a carman and reapired, rebuilt and refurbished cabooses for WP), foreign road cabs were common ON THE WP, but with other roads, it all depended on the pool agreements, usually with piggyback trains. Cabooses weren't interchange equipment however. Big difference. The ICC had standards that cabooses had to meet, however, the individual states also had their own requirements, California PUC's being some of the strictest. Also, Union rules dictated caboose design and equipment as well and so that caused some variations too. Some roads took immaculate care of their cabs (WP was pretty good about theirs), some roads had the most modern cars always, and some roads didn't give much attention or care to theirs. Some roads saw them as valuable working tools for their men, and treated them as such, some roads saw cabooses as a spendy nuisance (you know, like UP thinks of their real working employees

) and let their cabooses go to hell in a handbasket.
The WP had a train "SEALAND xx" (xx denotes date) (crews called it "The Seal" for short) which was a hot intermodal Container/trailer on flatcar train originating at Sealand in Port Elizabeth New Jersey and terminating in Oakland California, literally coast to coast. It was a land bridge arrangement for Sealand to avoid sending ships through the Panama canal for speed and efficiency's sake. It was from what I can recall one of the hottest trains on the railroad. On one fateful day in April 1980, the SEALAND 6 had 3 UP SD40-2's for headend power (Referred to as Extra UP 3734 West) and a D&H Wide vision caboose (#35791) that was a piece of @#%&. The caboose had NO working radio and bad wooden core doors that would stick, in fact, the rear most door was stuck closed, despite Dad's efforts to pry it open for the crew in Stockton when he air tested the train in the yard. The rear end crew was 2 good friends of Dad's, and one was a good family friend that was like a brother to our neighbor, we used to have pool parties where Mark would come over to Steve and Bernieces and I, being 4 years old and a TRAIN NUT, would ask him a zillion questions. He always patiently answered every one and was a hell of a nice guy with kids of his own. As a trainman (my Dad was a carman, so while his job was interesting to a 4 year old train nut, train and enginemen were GODS), I just found his job fascinating, so I'd talk the guys ear off.
Both guys told Dad to just forget about it, Oakland was afterall, only about 80 miles away and they'd be done with that caboose anyway. Fact of the matter is, that caboose was illegal for service in California per the ICC. That stuck door in an illegal piece of &*%$ caboose was what killed Mark and Eugene ("Obi") a few hours later as the caboose trapped the crew while a UP C30-7 from a "helper" consist lay on top of it at the bottom of a Hayward California underpass burning what was left of it down to the ground. I only hope to God their deaths were instant and they didn't have to suffer. I'm almost in tears writing this, as it was a very rough night for my family; Dad was the one that had to go next door and tell Steve and his family that their beloved "brother" had taken his last train out. (I get chills thinking about Dad coming back into our house right after that). Another good friend of mine was almost killed as he was the helper engineer that pushed the Seland 6 over the overpass and flipped the consist over and dropped the second unit of his consist onto the caboose. He had sustained a broken back and burns to his legs while his brakeman pulled him out of the cab, otherwise, he'd be gone too. All because management didn't want to take the time to refuel the Seal.
It was the blackest day on the old "Wobbly". It was a horrible series of mistakes by WP management that snow balled into a hellish nightmare for a LOT of people.
Here's a photo a WP employee had shot of the Sealand 6 at Midway, California on Altamont pass after the RBW-9 was combined with the Sealand 6 to push it into Oakland after the Seal ran out of fuel. An hour later, this train was a fiery mass at the bottom of Industrial Parkway in nearby Hayward. I won't post photos of the wreck here on the net, but I have a couple dozen photos of the wreck and the 36 Page NTSB accident report for those interested in reading about one of the main reasons why cabooses were NOT normal interchange equipment. E-mail me if interested in reading the report, but just a heads up, it'll **** YOU OFF reading about the disgusting actions of the management involved to "expedite" this train to Oakland. The shortcuts these people took cost two men their lives.
Folks, I apologize for the LOOOONG post, but I thought this would clear up some questions while giving you some insight to the daily workings of cabooses and what can go wrong when Management gets impatient. I'm sure Greg misses these guys alot, he worked with them, and on the WP, they had their own RR term for their fellow employees:
"Brothers".
UP 3734 West (Sealand 6) at Midway CA roughly an hour prior to derailment
RBW-9 pushing Sealand 6 at Midway