The La Mesa Model Railroad Club at the San Diego Model Railroad Museum has probably built the most famous model of Tehachapi. I think their track plan is published in the Kalmbach book "Walk Around Model Railroad Trackplans" by Don Mitchell, a member of the La Mesa club. I think their layout is either 1/3 or 3/4 scale in ho, that is they have modeled 2 scale miles for every three on the prototype or 3 for every 4. If you look at back issues of Model Railroader, Jim Kelley, one of their former editors now retired modeled Tehachapi in n scale. His layout was featured a few times in MR or one of their Great Model Railroads annuals.