Arabic in Lebanon

I'm watching "Caramel," which is a story which takes place in Lebanon. It says the movie's language is Arabic, but I'm hearing a lot of French words. In one part a seamstress and a customer even speak French as a lingua franca because the customer is Armenian. Is French a big influence on all of the Arabic-speaking world or is it strictly limited to Lebanon? Is the Arabic spoken in Lebanon mutually intelligible with Arabic spoken elsewhere? How diverse Arabic?