To carry forward from the Britain does not have a treaty with Poland thread that is now spinning off a bit towards discussion of the Maginot Line, I'll pick that up here.

The first issue that has to be dealt with is the Luftwaffe versus the French Air Force. Could the French in 1940 keep the Germans from attaining air superiority over the Maginot Line? I would say no, they couldn't. They lacked the equipment, tactics, and operational experiance to do so. Lack of a BEF AAF componet would only make things worse.
With the Germans having control of the air the French are really already hit. Their primary forward offensive artillery is not contained within the Maginot Line fortifications but rather is field artillery stationed with the interval troops. A near complete lack of AA guns is going to pretty much ensure that the Luftwaffe will silence the French guns in pretty short order. This would be a near perfect mission for Ju 87s.

As for the line itself, once the interval troops are pinned the Germans could readily and rather easily advance on the Line itself. The Line lacks antitank guns and relies very heavily on passive defenses to keep tanks from reaching the various fortifications. The French had no mines emplaced and were late comers to even developing this weapon. So, unlike the heavily mined Sigfreid Line the Maginot has little defense against tanks.
The lack of means to really stall a tank offensive, it is likely that the Germans could close on many of the defenses and simply shoot the various exposed cupolas and observation positions out leaving the defenders essentially blind.

Using assault engineers in gliders as at Eben Emael is also possible. Like the Belgian fort, the Maginot Line completely lacks antiaircraft defenses.

With the line breached, the Germans have the advantage in both tactics and air superiority to handle the interval troops. Without artillery the French using their slow and cumbersome doctrinal system would be at a severe disadvantage. I also suspect that there would be a bad blow to French morale if the Maginot Line went down in a matter of days. It would say that the fortifications were really pretty worthless and France's best defense was a poor one.

I doubt that it would prove even a truly difficult barrier to breech.