I dunno about Canada, but FRA required auxillary lights (ditch lights) deadline of 1994-95.
The following in a clip from an email from Al Krug, a hogger for BNSF in Sheridan, WY:
"In the 1980s the BN started replacing the yellow bubblegum flashers on
the cab roof with deck mounted strobe lights on the front of their
locos. But I don't think many SD40-2s got them. Mostly the LMX 8500s and
BN GP40s, 50s. The ditchlights replaced the strobe lights on those that
had them but the strobes met the FRA requirement for "ditchlights" (the
FRA does not call them ditchlights, that is a Canadian term, the FRA
calls them auxilliary lights) so the strobes lasted on some units a few
years after the 1994-95 FRA deadline for ditchlights. I believe the
first SD70MACs in 1994 were the first units built with ditchlights."
Maybe that will help!