RED: Same network range on UTM and RED?

Hello,

I have a following situation: two remote offices, which each have an IP-phone and two computers.

Now, my question pertains to RED: from what I can read here, even in Standard/Unified, the RED device is in it's own segment (subnet)? Correct?

Can RED also be in the same network segment as the UTM? It is possible for me to work with an additional interface, albeit more complicated, as I have to NAT couple of addresses from the RED-network in that case. The reason for this is that our UTM-network connects to another remote network, which only allows for access from the UTM network, and not any other. So I have to translate all devices that are in the RED-network to adresses in the UTM network. The important thing is that IP-phone addresses have to be unique and dedicated.

Can someone clarify please? Thanks.