Actually you can, but it's a huge pain in the ass. I live in an area where Alltel is still Alltel. After buying CDMA Workshop and hex editing certain parts of the phones memory, we've got one working almost fully. Trying to hash out the 3g connectivity issue. It works on and off... picking up an Alltel Hero to compare settings. When the 3g/EVDO actually works, it's fast and nice, but it just doesn't stay. I think it has something to do with mobile IP vs Simple IP settings. I honestly have no idea. I'll post back here if I figure something out.
Also, we were able to call our Alltel business rep who was able to add the MEID to one of our lines without issue, no illegal things happening here...