I took a look through the latest California Railfan Timetable (No. 20), and this is what's on the main line: after CP SHELL, Oceanside station is MP 226.4, CP ESCONDIDO JCT., where the siding ends and the crossover to Sprinter begins, is 226.8, and CP LONGBOARD is 228.4. If you stand on the Sprinter platform (Oceanside Transportation Center, MP 99.3, and I haven't been able to figure out where that's measured from; the mileage increases toward Escondido), looking compass south, the first interlocking is CP OCEAN, 99.5, where the two platform tracks merge into single track, and the next is CP RAILROAD, 100.1, where the crossover which left the main line at CP ESCONDIDO JCT. and I believe generally corresponds to the original alignment of the branch before Sprinter, joins the present Sprinter. The south leg of the wye, which leaves the main line at CP LONGBOARD, comes in from the right at CP WYE, 100.3, which is immediately east (compass and timetable) of the first station at Coast Highway. In other words, the interlockings on the main line are SHELL, ESCONDIDO JCT., and LONGBOARD, while those on Sprinter are OCEAN, RAILROAD, and WYE. I'm planning to go through there on Monday and will try to see as much as I can from the train. There is a nice enlargement of the layout at Oceanside on page 62 of the latest Steam Powered Video atlas of California-Nevada. (The interlocking I always got a kick out of was CP CUMBRES, formerly Miramar--I thought I read recently (maybe on this site) that they were going to change it back to CP MIRAMAR. Some people have no sense of humor.)