It depends. IF they are still being paid by the company, the no compete can indeed still be in force. If, however, the employee negotiates a release from contract with a certain payment plan, it might be nullified or shortened.
Say, for instance, a person has 4 months remaining on a contract and the company wants to pay them for the four months and maintain the 6 month no compete, that would keep them off a competitors air for the 4 months PLUS the 6 months of no compete....
If the employee were to negotiate no payment for remaining time on the contract in lieu of tearing up the no compete, then the individual would be eligible to go elsewhere immediately. Of course those terms could be worked either way with more or less payment time / no compete time.
One time when I left KLUV, I had heard all these arguments about stations no compete not holding up. Well, I went to a well-known law firm in Dallas and they took a look at it and said, "sorry, you signed it willingly", nothing you can do other than try to negotiate with them. I ended up getting a parttime gig at KEGL and asked KLUV to allow me to work there since it was not in direct competition. They agreed as long as I compensate THEM. I thought it was CRAZY until they said the amount of compensation was $10! It was their little way of making a point I guess. I didn't like it but I gave 'em a ten dollar bill and went to work.
The main lesson is be careful of what you sign. It's natural to want the gig so bad that you are tempted to sign on the line and get back on the air, but you'd be well advised to always ask to take the document home and look it over. You would be even better advised to have some legal authority take a look at it and explain fully what they are asking you to sign. Few actually do this but it is rather important, especially if you do not wish to move out of the market if your gig doesn't work out.
If they give you grief over taking the document home or say the document can't leave the office or somesuch, you then have to ask yourself, do you really want to work for people like that?