We have intermittent issues with OOF
What exactly do you mean by that?
OOF is not in any way dependent on Blackberry or BES. So if you switch on OOF on Outlook, the Exchange server will serve OOF replies.
The only part where BB comes into play is when you switch on OOF via the BB. This should then switch it on on Exchange.
So what are the exact intermittent issues? The sync of OOF from BB to Exchange. Or are OOF messages not going out intermittently? Please be as precise and detailed as possible.