I don't know about Santa Ana, but the Oceanside power was rotated with San Diego units by the 4th District Local. San Diego had a mechanical foreman, so they might have done the FRA inspections, but anything more than minor repairs probably went to San Berdoo. Both the SDX and Night Coast were usually short on time, especially if they had to double Miramar Hill (which happened often - they used the manual crossover in the middle of the two main tracks on the San Diego side for this move).

By the early 80s, CF7s were the usual power for the switchers and locals out of San Diego and the Escondido. About once a year, the Escondido would start a grass fire on one of the grades because the units had just been rotated out of San Diego, and were all carboned up from being switch engines. IIRC - one of the local fire departments even scorched their fire truck one year on a RR fire around San Marcos.

After the CF7s started to leave, the combined Escondido/Miramar local got any combination of GP20/30/35 rebuilds, and even a few small B-B GEs. The only 6-axle unit I ever saw on the branch was a SD24(?) with an FRA geometry car.