Can multiple domains use a single RDP License Server?

Hello,

I have an odd situation.  We have our primary domain that has 25 RDP licenses and only 12 users.  We have another group joining us that I want to put on a separate domain.  They will have a single server that will primarily be used as an RDP server.  Can I use the other domain's RDP Licenses, or would the new server have to exist in our domain?

Thanks,

Jeffery Smith