Can I install a VRU PG to interface with a 3rd party IVR on a standalone server and use it with system IPCC or will I have use the enterprise deployment? I have an IP-IVR for queing
You would have to use the enterprise deployment to use the 3rd Party IVR. The System IPCC deployment is very CallManager/IP-IVR specific - it can't even use Cisco Voice Portal.
If all calls should go through the 3rd party IVR before arriving at IPCC, there may be other options to have these calls handled, such as terminating your PSTN ingress on the IVR, or routing calls through the IVR using IP, although you would invariably end up with some call-tromboning using these methods.