Hi
First you can use the same pool and same OCS Server for both RCC and EV (looking at your post seems to say you created the second pool just for that).
As you need the same Location profile for Exchange 2007 and OCS 2007 EV integration, there could be an issue with your need, no tested yet.
You talked about "a dedicated phone route to another gateway for this pool": you said this second pool is for EV, so gateway meens Mediation Server. if your fist gateway is he RCC Mitel equipment, these 2 gateways have nothing in common, for the route I mean. So if you don't need more than one Mediation server, one route will be enough( for EV mode).