No it can not. At&t and T-Mobile phones run on system called GSM. Alltel, Verizon, Sprint, US Cellular, etc run a system called CDMA, two different types. There are currently no dual CDMA/GSM phones that run on the frequencies used in the US readily available to regular joes. You can use it on T-Mobile, but you would have to have it unlocked first.
Even then Alltel probably won't activate it and if it does get activated the OP may not even live in an area where Alltel (or one of the companies they bought) had TDMA coverage so he probably won't be able to use it anyway. Probably your best bet it to buy an Alltel phone from the company directly or from eBay.
