MBB Connect allows you to tether your phone to a computer and use it as a modem. It gives you 5GB of use. It can be removed at anytime.
On a different note, do you use your email in the Tour for personal use or do you need to use the Blackberry Enterprise Server(BES)? The $44.99/month(BES) is auto added when a blackberry is added to the account, but if you are just using personal email like gmail, yahoo, hotmail you can change to the personal for $29.99/month. It gives you the exact same thing you are already using.