I went on a 1 day CSI course in Halifax(?) recently...excellent course, highly recommended - run by former and acting senior officers of Greater Manchester Police, etc. Anyway, one of the questions we raised was about how police allocate their resources, eg, divers, sniffer dogs, etc. The reply was that years ago, every force had its own divers, dogs and other specialist teams.
Nowadays, they are either pooled between several police forces, or outsourced to external operators. They have to literally order a dog/diver/excavation expert in. My husband asked about whether cost of the operation is ever in the lead officer's mind in cases such as this. The response was "no", but they do try to barter resources to save money. Eg, if a force A needs a sniffer dog, they might say to force B, hey if you let us use your sniffer dog, we'll give you our diver for free next time you need one.