For northbound trains, these will "almost always" be on trains 207, 211, 217, 231, 261, 267, 275, 277, 383, 287. FWIW, I consistently see bumps on northbound 323, 225 and 329 in the South Bay, generally in Sunnyvale or Mountain View.
Southbound trains with two bike cars will be trains 210, 312, 216, 220, 228, 230, 362, 266, 372, 378, 386. In the evening, I sometimes ride #266 (got bumped once last summer), and I can almost count on getting bumped from 264, 368 and 372 in Palo Alto when the weather is nice.
The two bike cars are not guaranteed as Caltrain may be constrained by equipment malfunctions and "other operational needs." According to information from today's meeting and now published on Caltrain's website, these trains will consistently be Gallery or "old style" trains, which have a much higher capacity that the newer Bombardier cars.
At the meeting, Caltrain staff also said they have signs planned that can be mounted to the front of the train so cyclists waiting on the platform can see if an approaching train has one or two bike cars.
Caltrain also said they plan to convert the two non-bike cab cars in the fleet into bike cars as funding becomes available. Currently, two of the Bombardier cab cars are not bike cars.
Finally, Caltrain staff said they have a design in mind so that bike capacity can be increased to 24 on the Bombardier cars that sacrifices only four seats, instead of eight seats as originally thought.
Thank you to Murph for liveblogging this information from the JPB meeting this morning. Thank you also to Ravi for publishing some of the updates to Twitter/bikecar.