I'm not sure if that scenario would work, depending on the power layout. Chances are you have a service feed going to both, rather than a subpanel feeding off of either... in which case you would run into a problem if they hit a transformer.
800M away is also of significant difficulty... do you have conduit in place to link the two?
If so... you may want to try to pull in a category 3 or higher drop between the two, place a protector on BOTH sides, adequetely grounded to meet requirements for your area, and then try a point to point DSL solution, Paradyne makes several products that will meet those needs, and there are a few documents available on the web describing how to use Efficient (aka flowpoint) SDSL bridges to communicate point to point.
If the power solution works, that would be super -- and go that route, much easier.
Fiber would be a challenge, although you could buy a preterminated cable to spare you the expense of termination... you'd need to pull it within tension specs, and also use a special pulling eye/sock combination to protect the preterminated connectors.