I have a 4 year lease for a chevy tahoe that is through bankone.  I like the Tahoe and probably want to buy it.  The lease had a fixed buy price.  Is this negotiable?  Who with, bankone or the dealer?  

With whomever is carrying the note, in your circumstance, Bankone.  Suntrust came off the residual on a leased truck that I had by almost $3000.00.  That was the only way that the deal could have worked and been economically feasible for me...It's also possible that Bankone will not negotiate and you would then most likely be better off buying a new, or at least newer, model...

GLOCKshooter
You want to contact Bankone. If they tell you they can't do anything on the buy out price go higher and ask for a supervisor.
Blackgun  

I'm not familiar with BankOne's policies, but a friend went through a similar experience on a Jeep he leased..through Chase Manhattan.

Chase started calling him about 4 months before the end of the lease asking if he was going to buy it. Each time he said he doubted he would, but out of curiosity what was the buy out price.
As the time to the end of the lease approached, the price dropped. With a few weeks left, he called them and made them an offer. At first they refused, but the closer it got to the end of the lease, the more they were willing to negotiate. He ended up buying it out for thousands under the buy out price listed on the lease agreement. The last thing the leasing bank wants is the car, which they will have to sell anyways..

Play hardball with them. Really low-ball your offer and don't negotiate higher..let them come down until they get to a price you like.