Back in February I wrote a post about BART getting WiFi service. Last time I flew through SFO, I decided that I'd play around with the wireless signal when I was riding on the train. In a nutshell, the signal was only available in the underground stations in downtown San Francisco from Civic Center to Embarcadero. I was really hoping that that the signal would be available while the trains were moving, but unfortunately, no luck. Just keeping a signal a few feet after leaving the stations was an impossible feat for my cheap Linksys wireless card. Below are a few screen captures from the connectivity in the four station run.
1. The SSID's available as we rolled into Civic Center Station
2. The captive portal login screen
3. The SSID's available at the Embarcadero station, just before hitting the Transbay tube
The cellular providers use the "leaky coax" method to distribute cellular signals in the 800 and 1900MHz bands in the tunnels, so I don't see how hard it would be to do this at 2.4GHz. A caveat as well... I took this trip back in early May, so they may have improved the coverage since then.
This better be the pre-alpha testing, or they are going to have problems with their long term plans...