Legally speaking, the titles have to be at LEAST two letters apart.
Besides, if Telltale names it: "Fables: The Game", they're good to go.
The fact that Fables the comic series appeared before Fable doesn't matter, since the entertainment fields are different.
Fun fact: I have a 5 year old secret project. I got an international trademark on its name, in various fields. Because of that, a foreign game had to change its name when it was localized in Europe some years ago. ^^
I would love to talk about this project, but I want to film it first. Unfortunately, I lack the funds to do so. It was estimated at over 1 million dollars by two different professionals, so I needed to find a smart way of reducing that price. Which I did. I'm just looking for actors now.