I was wondering the same thing. I do most of my credit rebuilding while I'm at work. Only during down times that is! Lol. Anyways where I work every phone line is recorded for safety and security (aviation related). If I told the CA that my line was recorded could I then use that conversation as leverage if they didn't hold up their end of the bargin? Would that constitute an oral agreement?
Starting Score: 574(may 2012)Recording is only legally useful if the CA is harrassing you or calling you names, etc. The CA is under no legal obligation to remove your derogatory information from your CR. You would be hard pressed to find a judge that would be sympathetic to your case.
The only use that the recording of the call might have is that you may get lucky and get a person at the CA on the phone that does not know that you have no strong legal recourse with the recording and therefore be more inclined to make sure the deletion happens. So, that being said, it couldn't hurt. 
Thanks for the input. Here's my scenario, I,think I'm going to have to bring legal action against 1 creditor: Pioneer military loans, $3375 DOFD was 4/2006. Charge off 9/2006. So drop off date was roughly 3/2014. Then in 9/2009 they made it appear that I had brought the account into good standing (I didn't. Last payment I made was 3/2006.) 10/2009 they beging to show the account past due again. New charge off date 4/2010. Making drop off date 10/2017. Same thing happened 6/2011 and now drop off date sats 1/2019. I've been gathering recorded messages where they all but admit doing this. They explanation was they wanted to give me a chance to fix my history With them. Last time I had any contact with them before now was 4/2006. Edit sorry I'm writing on my iPad and it,doesn't register the sentence separation for some reason