I drive through that gate dozens of times each year, and you have to look to notice that on the far right is a "pass lane" for people that are not stopping in Banff or have an annual pass.
However, if you even stop in Banff townsite to gas up or buy a coffee, you're supposed to buy a permit. It's not a toll to use the road, but to be inside the park. This is why bus passengers have to pay as well of their tour bus is stopping in Banff.
I e-mailed Banff National Park and here is their reply:
"When you are only driving thru the National Park via the Trans-Canada
highway and you are not stopping,you don't need to purchase a national park
pass. If you stop to do some shopping ,or sight you will need a pass, stopping to
purchase gas, bathroom, or food is allowed."
So if I read this right, you can bypass the Park fee if you are not stopping in Banff or campsites; and you can fill up with gas or go to the bathroom along the way without paying the fee. I'll make a revision to the article to correct it.