In my opinion, anytime you combine services and work with other orders of government, it makes sense. However, you also have to have the assurance that those levels of government are not going to bail on you three years later or five years later.
We have combined services in Newfoundland and Labrador in various areas. It's not a far stretch to see the post office combined with other government services in any order of government, whether municipal or provincial, in these smaller communities. Whenever you can rationalize services, then it makes sense to do so if you cut the costs and still provide the same service at the same level of quality.