I for One would say it depends on the snake.
Most toilets run either a 3" or a 4" ABS pipe out to the sewer line, Then the Sewer line itself is any where from 6" and up.
we all have heard about sewer rats so right their would be a good food supply.
And on futher note about toilets they hold only a slight amount of water in the back to keep gases and other vapors out of the house. and if the sewer line is correct then it will have a slight fall to it, I know that the min. fall used to be a 1/4" per 100 feet.
So Again I would say it is possible.
EDIT:
I think this can show a good anwser.
YouTube - Bad sewer pipes across America
