3 weeks or 3 months, page-10

If it was a rat, it probably shorted out the switchboard (they get in behind the high voltage circuit breakers sometimes), resulting in an explosion & small fire.

There's not much a rat can do to damage a transformer directly.

I doubt the transformer would've been damaged (in the case of a rat), as it's usually in a different room to the switchboard, and the incoming circuit breaker should've tripped out. This would isolate the transformer & switchboard from electrical supply (& electrical fire).

If the rat ate through some control wires (or a high voltage cable), then the damage to equipment would/should be a lot less.

In most cases, I'd say 2 weeks should be plenty of time to get everything back up & running.