Unfortunately, I don't think there is. The OPC Interface treats InstrumentTag as a string. If the InstrumentTag doesn't exactly match the ItemID, the interface just rejects the tag. There is no configuration to make this mechanism smarter. Perhaps you could contact tech support and create an enhancement request.
Only other way I've seen this overcome before is to collect both sets of data then have another tag (PE or AF) sat on top which determines which value to collect based on the active server. That's ok for a small system but not so good if you have a limited tag license and is also a pain if you need to add more (Excel concatenations can help though ).