I have no idea! Obviously streaming is heavy on bandwidth and I don't stream to my phone so I won't know exactly how much (say 2 hrs of rugby) streaming would consume. Some people use Onavo to monitor data usage, but I uninstalled it as it would not give me accurate figures. Also, I flash (way too) often, so it was never a help to me. ICS has a built in monitor which might help you, but again, I found it not to be too accurate (this is not available on GB).
The bottom line is - you can stream now, but you must find a way to monitor your data. There are apps on the market you can try, but I honestly do not know how good they are. Perhaps some the other more experienced guys on here can help out with an app. Also, take a look at
this thread.