T-Mobile confirmed today on Twitter that subscribers currently running on legacy data plans will be allowed to keep their existing plans when they switch to T-Mobile’s upcoming iPhone-compatible HSPA+ network later this year, rather than being forced into tiered data plans like those offered by other carriers.

This is a huge confirmation for many T-Mobile customers, because it means that anyone still using one of T-Mo’s old $5 unlimited 2G/EDGE data plans will be able to get $5 unlimited HSPA+ 4G on their iPhone when T-Mobile finishes refarming their 1900 MHz spectrum later this year.

Thanks Scott!