Sorry, should have clarified. You were saying that you can easily upgrade to just push email and use that with blackberry, however this push email service is for exchange, and won't work with a blackberry. blackberry have their own push email service, which is separate from exchange.
However, you are probably correct in that Three, especially if you are paying a high price anyway, won't mind you moving up or sideways in terms of contract amount.
But saying that, that is not always the case. Like many things in HK, HK companies are not always as flexible as you think. To them, once you have signed a 24 month contract, they will not let you vary it under any circumstances.
You're right, of course, I'm now thinking back the the nightmare I PERSONALLY had installing BES on SBS. I think I'd formed a mental block for that whole sordid affair - I think we can safely say from all of that the best response would be "Cheers for the convo starter, your best bet's to go and have a chat with 3..."