Sign up for an account with 4smartphone.net and set up email retrieval to pull in your corp mail using POP or something. Not exactly elegant, but if they won't turn it on for you, what can you do?

FYI - a buddy of mine told me yesterday that if OWA is enabled, chances are good that pushmail is turned on as well. Just punch in your OWA server name when setting up the handset and see if it will configure itself. It's worth a try.