I'm using Odoo 9, but I think this applies to all versions.

We have 'pos_config_id' field on the restaurant_floor table, so floor can only belong to one Point of Sale. On another Point of Sale I cannot select existing floor plans.

I might be wrong, but I see POS object as a cash register (please correct me). Is it possible that this module doesn't predict a restaurant with more than one cash register?