VPN-One tunnel, three routes

Our company has a client who has a managed VPN with a third party. The third party has one public IP address to establish a tunnel. Right now, we have a tunnel established, and the private routing goes from our private subnet (we will call ‘localsubnet’) to a specific address on their side, which is a domain controller (we will call ‘remotesubnet A’). However, they want to add ‘remotesubnet B’ and ‘remotesubnet C’ to also be able to access ‘localsubnet’. I have tried to set this up as having the same Proposal and Peer with separate Policies, but what happens is, whatever policy gets established first, the router sticks with, and the other routes don’t work. Is there a way to make them all work?