I don't necessarily think this is what he meant, but generators can sometimes be operated in synchronous condensing mode. In this mode, the generator is run as a motor, which consumes real power but can help with reactive power issues important to grid stability.

No, electrically generators and motors are the same circuitry. If you have two generators hooked to the same output line, and one gains a few degrees of phase angle on the other, the one lagging draws power from the leader in proportion to the phase angle difference.

Yes but with a bit of electronics you can stop this from happening. Source: Institute of Physics.

Curious what electronics will prevent a flow of AC electricity.

This is what is used in the UK: http://en.wikipedia.org/wiki/Synchronization_%28alternating_...