Can an electrical wiring system carry enough current to create an EMP?
Interesting concept. I don't know how familiar you are with electrical engineering, so forgive me for perhaps being too simplified. I have been told (anecdotal) that modern systems are much more resilient against actual EMPs because of the smaller sizes internally. 

I would imagine that the average datacenter has extensive surge protection (to survive things like lightning).

In addition, I would imagine that Police forces have gear that is resilient against such attacks, precisely to avoid being vulnerable to this type of attack.

Now as to your questions: 


  Could the average datacenter electrical wiring carry enough current to create an EMP?


The current carrying capacity is not what matters here. In order to generate an EMP, you need to be able to create a sudden surge/pulse of massive size. Every circuit has a certain inductance - the inductance is a measure of how much a circuit resists sudden changes in current. This inductance is what could prevent this from working. 


  Would circuit breakers or fuses preclude the surge's EMP effects?


A datacenter would have surge arrestors to prevent surges damaging their equipment. They do this to protect against sudden spikes in the network due to faults, lighting, etc.


  Would the electrical power surge damage the electrical wiring and electronic devices commonly found in an average datacenter?


Without protection, indeed they would be damaged. However, as already mentioned, datacenters have to be able to take direct lightning strikes without issue. If they can take that without being absolutely destroyed, I doubt anything short of a nuclear EMP would be able to damage them. Same holds for the police equipment - their stuff should be able to handle such surges as they would have to function after an attack or disaster that causes an EMP.