Simply, no.
They could have disabled it in more than one place and it sounds like they won't turn it back on.
You could use something like the MobileMe plugin for Windows as that does some sort of syncing, but that assumes that the necessary ports are open on the corporate firewalls.
As said you could publish you calendar to some sort of web based service, other than MobileMe, but you will probably find that this is in violation of your companies IT Policy. You would also have to hope that your iPhone can sync with said online service.
Maybe a sync through iTunes?