Zukharla wrote:
It definitely depends on the horse. We had a huge Percheron gelding once that we bought from a beginner rider. He was lazy and had learned, in a round about way, that if he bolted on her, he'd get out of work because she's get scared and get off. Once he bolted, he'd set that thick neck of his and you couldnt turn him or stop him. He did it twice on me. The second time I realised WHY he was doing it after talking to the old owner more and I made that idiot run and run hard. He never bolted on us again and is fine with his new owner too (who I made sure was NOT a beginner).

I am not saying do this with this particular horse, just saying that bolting is not only an attribute for 'hothead' horses. The horse above was damn lazy and saw it as a way of getting out of work.
I had a mare with a bolting habit that I fixed in the same way. If she took off, I would put her on a massive circle and make her run until her knees melted, and it worked. It sounds as though the OP's horse is more dangerous than my mare was, though, if it's trying to run her through fences. As a work evasion tactic it seems pretty extreme... like you said, it's hard to know without seeing the horse, but I'd guess that it's a bit more than just getting out of work.