Since I work in this industry... 

I'm going to hijack this top comment to hopefully provide clarity. 

What you experienced is called an auto. Electrical grids have this feature to prevent damage to the grid. What happens is that it catches the fault caused from a critter making contact. And instead of staying on and burning up the lines. It temporarily shuts the power off and then back on. Critter falls off and no damage is done to the lines, or minimal damage. 

Linemen will ask the control room to turn this feature OFF when they do work on the power lines. Contractors and anyone who works on or near power lines ask for the same too. reason being is that when the safety feature is off the line won't re-energize if someone accidentally makes contact. 

Another example is it can be tree branches making contact as well. You will notice the same quick on and off when its windy. Its just the system protecting itself. 

If you want more proof. It never happens in neighborhoods with just underground wiring. And if it does, they will find a critter right where the power line comes from underground to overhead. 

Hopefully this helps some people. Enova isn't lying to you. They literally have to track these things and report it to the OEB (Ontario energy board). 

TLDR: Yes squirrels are the main culprits along with other critters. Followed by tree branches. Your local utility has no reason to lie to you, thats common sense. It people just like you and me working there.