As Stash said, lots of passenger trains on the UP (Capital Corridor, San Joaquin, Starlight, Zephyr), over 30 a day. A lot of freights runs at night, but also tend to appear during the mid-day passenger lull. (Sometimes they show up during prime passenger time as well.) Good places to fan the UP include Victoria Park in Hercules, Eckley Pier Regional Park just east of Crockett, and the Martinez depot. All are public access right at trackside. UP is two-track CTC, trains can run either direction on either track. Talking detectors at 14.1 (east of Richmond), 27.8 (between Crockett and Ozol), and 31.3 (just west of Martinez depot) can be very helpful.

Traffic on BNSF is more sparse. The early part of the day can be rather dead, with traffic picking up in mid-to-late afternoon (subject to variation, of course). They dispatch by track warrants, but eastbounds out of Richmond can get them off a printer instead of the radio. (Of course, more may be issued enroute.) There's a talking detector at 1180.5, where the tracks go under Interstate 80 in Hercules. There are some good places to shoot in Hercules, including the berm behind the Home Depot, the west end of Collier siding off Sycamore Ave., and Christie Road off Highway 4 east of the golf course. (Note that you can only access Christie Road from Highway 4 eastbound; if you need to go west from there, there's a full set off on/off ramps at the top of the hill.) Being able to view both railroads from one spot in Pinole is no longer possible due to fences and grown-up trees and brush. Hope this helps and good luck.