BCL
Engineer
Apparently they've been testing the sets (Stadler EMUs) for months, but they'll be going into revenue service this weekend with two trainsets. They have't announced on what train numbers as they apparently don't want a crush of railfans crowding into these trains.
Dan Lieberman, a spokesperson for the agency, told SFGATE that they decided against announcing which specific trains would be electric on Sunday — as not to crowd them for safety reasons or displace regular riders — but said there will be “a couple” electric trains in service. Moving forward, until the official launch of the entire fleet next month, Lieberman said Caltrain is “introducing more electric trains every week.”