When I was working in SW Virginia a few years ago, there was an 8 month wait for a new patient on Medicaid to see a shrink. This should be interesting to watch.
There is already a shortage of psychiatrists, in part because of miscalculations about the demand for psychiatrists by the gov't and cutbacks in funding for mental health training that occurred years ago. AFAIK the mental health insurance parity under Obamacare is nothing new. This is only the regulations about it. I mentioned insurance payment parity to my cousin, the psychiatrist, a few years ago -- and he just shrugged and indicated that it didn't make much difference to him, since he already had more work than he could possibly handle, and he felt it was his patient's responsibility to deal with their insurance companies.
More increased demand with a decreasing supply under Obamacare. As you say -- this should be interesting to watch!
In my area the wait is ∞, with no psychiatrists accepting new government insurance patients at all. There are very few practitioners in the psychiatric specialty. This is although every other conceivable specialty (cardiac & cancer & neurological centers, etc.) is way overbuilt with excess capacity.
If one can make do with an ARNP in the psychiatric specialty the wait is six months.