A bit of background is necessary on the 'doc fix', starting even with just what it is. To greatly simplify, standing law has reimbursements to doctors under Medicare being slowly shaved down over time. But Congress sets the cuts aside every year. So it's one of these things that is already a reality. It's just that the government and its accounting pretends this cut law is in effect, when in fact Congress always votes not to enforce it.
Democrats have made no secret of the fact that they want to change the law outright -- which is little more than making the current reality official. And pretty reasonably they say that it doesn't have anything to do with the Health Care Reform legislation since it's not like something that makes this bill cost more.
So what does that tell us about the disputed memo? Hard to say. One thing that's weird is that the memo seems to buy into the idea that the 'doc fix' is part of the Health Reform legislation, which does not sound like something a Democratic aide would say But again, very hard to draw any conclusions. All we know is that Dems are furiously denying its theirs.