Yes it is (I think)
You would need to configure separate IP addresses for each card and each machine. Don't use automatic IP allocation or DHCP (off a router).
So for example you could have
MacPRO - NIC#1 IP: 10.0.0.1 (VEPRO Traffic)
MacPRO - NIC#2 IP: 10.0.1.1 (RDP Traffic)
PC NIC#1 IP: 10.0.0.2 (VEPRO Traffic)
PC NIC#2 IP: 10.0.1.2 (RDP Traffic)
Also set the VEPRO NIC to be higher in OSX network stack (i.e. move it to the top)
Also ensure you are using a direct connected ethernet cable (i.e. no router in the middle) and that each route has no default gateway specified otherwise the computers get confused.
Sorry if that's all a bit techie...
Tim