If you're looking at the Beeb then you probably have the latest news available to general public. Unless somebody here has family etc in Chile and can get more info out...

Given Santiago's inland location, unless there was substantial liquefaction I'd expect mainly cosmetic damage to the Metro. Ditto with BART - unless a quake is on the Hayward fault cutting the line, I'd expect mostly cosmetic damage to BART though the Bay tube might need a little realigning. Biggest problem is likely getting all the panicked people outside. Biggest structural/operating/getting restarted problem for BART would probably be water buildup from leaks and lack of power to keep pumps running. Also, trains seem to be easier to get going again (if slowly) - after the Northridge quake Metrolink was able to get commuter trains started to Palmdale within a week while the freeways took months to get even partly repaired.

We'll probably learn some interesting things from what collapsed and how in this quake, including any effects on the Metro. If one line is running already then damage to it is probably minor. From the pix in the news the freeways and some newer buildings don't seem to have done well. Most of the total collapses were older buildings as expected. I'm glad it happened at night though; the image in one story of the pancaked garage and all the car alarms going off inside the rubble is just amazing, but I'm glad it was probably only cars in there at that time of night).

A quake the size and type of this Chilean one is likely in CA only at the far north end of the state (bye bye Eureka when it happens - last time was about 1700 per geologic studies, Native American stories, and Japanese tsumani records, and some studies suggest 300-500 year recurrence) with most effects in OR & WA. We'd all feel it, and there would probably be scattered damage as far away as Sacramento and the Bay especially in high buildings. I've seen studies showing that the biggest Moment Magnitude quake likely in the S.A. system itself is high 7's (SF 1906 has been recalculated as 7.7-7.8 on that scale) - enough to cause a lot of damage but not nearly as bad as a 8.5+ subduction quake like Chile (and very occasionally N. Coast CA) gets.