On Tuesday, though, T-Mobile made that network upgrade official throughout the Bay Area as well as in parts of Arizona and Florida. T-Mobile CTO Neville Ray wrote in a blog post that it has switched on HSPA+ networks over the 1900 MHz PCS band in San Francisco, Oakland, Modesto, Stockton and across Silicon Valley. It’s also completed the upgrade in Phoenix, Mesa and Tucson, Ari.; as well as in Miami and Ft. Lauderdale, Fla.

That makes 15 cities in total where T-Mobile has “refarmed” its old 2G spectrum for HSPA+ (the other five are Las Vegas, Kansas City, Baltimore, Houston and Washington, DC). But expect the rest of T-Mo’s network to be converted quickly. T-Mobile has to complete the HSPA+ upgrade nationwide before it can start turning on its new LTE network in the second half of 2013. T-Mobile’s Ray has also stated the carrier will have a “material” HSPA+ footprint at PCS by the end of the year.

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