i wouldn't count on it.
firstly, the evdo modem is a plug and play windows device. i don't think you can make it run on the xbox directly.
secondly, i don't believe the xbox has an options to go online with a shared internet account. maybe there is, don't know.
more importantly, the ping times are gonna be horrible. just because it's wireless, i guess you should add a 100ms ping extra. in my opinion, evdo would be horrible for online gaming.
on speedtest, i know i got a ping of around 240ms on the lahore server, whereas i've gotten 100-110ms max on my dsl and even as less as 70ms.
go for a wired connection.