I'm always a little suspicious of the "doctors won't take them" assertion, since it reminds me forcibly of the "we're about to run out of baby catchers" argument. OB/GYN doctors mostly switch to just GYN when they can -- yet we never run out of people wantingn to catch babies. The docs _say_ it's because their insurance premiums went up, but that's a marginal impact compared to the scheduling issues (very, very, very few calls on Christmas to come do an emergency well-woman visit. As in, none.).
It turns out that there are doctors that take Medicaid patients and doctors who don't. The doctors who do are happy to take more. The doctors who don't don't want to take any. And reading the analysis reminded me a lot of trying to zone increased density: it's _way_ easier to get a relatively dense city neighborhood to tolerate a big increase in density than an exurb (and a 50% jump in density in a city neighborhood is way more people than a 100% jump in density in an exurb). The practice composition turns out to matter, too: big, hospital affiliated practices take Medicare/Medicaid; small practices don't (or maybe only take Medicare and then moan about reimbursement rates constantly).
Given the direction that practice composition is going overall, it's pretty easy to predict how this is going to turn out on the primary care level.
The problem, of course, involves specialists and access to them. That's going to be a tougher nut.