Network testing is hard work. You need to ensure coverage, regular data rates, and spread. That’s probably why T-Mobile happens to be testing their 1900 MHz HSPA+ signal around the Moscone Center in San Francisco just in time for WWDC.
Quoth T-Mobile to 9to5:
Arguably the time and location could feasibly be coincidental, but I doubt it. Where better to test connectivity with a band of iPhones than what amounts to the San Francisco iPhone Festival? As mentioned above, 1900 MHz HSPA+ service should be popping up in other locations across the country although I suspect T-Mobile will focus on markets where users are underserved, techie, and would love to spend $30 on T-Mobile’s unlimited data plans.