Peplink wants its pound of flesh, either primecare, or fixed licenses. For the BR1’s that aren’t on primecare you would need FusionHub licenses… I don’t know at what cost. Larger central servers (like a 310X or 580X) come with more licenses, not the Soho.
I don’t know what other systems you have, if you use cisco or juniper router/networking you caould connect via IPsec vpn… You really don’t want VPN… you want your two service providers to have a meeting of the minds… Schedule a technical session with the wireless telco and the server group and ask “how can we make this all work in the best way”