Month-to-month in Moscow?

I've got a question for the road (or, well, air) warriors among you. I'm going to be spending September through December in Moscow (with a couple of trips to St Petersburg) for work, and though I don't think I will need to worry too much about email, I want to have Google Maps available for getting around. So, rather than picking up a dumbphone, I'd like to pick up a reliable local SIM that isn't too exorbitantly priced on pay-as-you-go for texts, calls, and data. The Photon is quad-band (if I recall correctly), so it shouldn't be a problem getting it to work.

(I also noticed that Yota has WiMAX service. So this is a little off-topic, but does anyone know how hard it is to get Sprint 4G devices to roam?)

Alternatively, I have a Blackberry Tour that is unlocked and can work overseas - any idea if BB service is common and an easy add-on for PAYG plans?

I know that I can find prices online; that's not my issue. I'm looking for any tips from locals or travelers on reliability and possibly perks.

Thanks guys!