Negative. Does not work with the even more plans. I had to change my old family plan. Had to bump up the minutes and was looking at the even more plans. Store and online I was told if I want to add minutes I would have to go to an even more plan and would automatically loose my old t-zones unlimitted.
Called and found somebody you could just add more minutes to my plan (500 for $10). She tols me that she would have to change my t-zone plan to unlimited web (bummer, since I had the 4,99 t-zone) for 9,99. This is NOT COMPATIBLE with any even more plan. On those they want you to use the data package (for 30).
So if you have ab old existing plan you can add unlimited web for 9.99, either online or over the phone. If you call, just tell them that you have an unsupported phone.
Funny, when switching from t-zones to unlimited I had a down on the data for a couple hours to I called tech support and the guy goes: "so how do you like your N900". I was amazed how he would know what phone I has and asked him. He: "we are the tech support guys, and not the hotline in India. You use a phone on a t-mobile network and we know what you use." Guess they match the IMAI. So t-mobile does now that you use a smart phone. They just don't care as long as it is not one of their supported phones. Don't ask me the logic.