[basilray]

Here's a recap of the steps that I found on howardforums.com:

1. Obtain a Boost CDMA phone - MUST BE CDMA - NOT iDEN!!!
2. Activate the Boost CDMA phone
3. Switch to $50 everything plan
4. Wait at least 1 week
5. Call Boost and tell them you need to swap phones because your phone is not working, is broken, lost, what have you
6. Give them the ESN for your TP
7. Pray/Sacrifice Goats in hopes that the rep will activate the phone
8. The rep should walk you through reprogramming the phone for Boost which is more or less the same as reporgramming for Sprint

Apparently people have gotten this to work with the Mogul, Centro, and a few other phones. Rumor has it that some people have gotten TP's to work.

I wouldn't call this illegal...but it is definitely abusing a loophole in the system.