First, I can personally tell you as a DO, a 260 doesn't get it done. The bias is too large and actually borders on outright discrimination. I even received an email from a program stating they didn't take DOs for neurosurg nor did they know of any programs that did and that I should "be sure to check first before applying." They even graciously advised me that I should pursue general surgery. There is even a preference for carib. over DO from what I personally noticed on the interview trail. Hopefully, 5-10 years down the road, this will not be the case. There have been DOs that have matched but it seems they were special circumstances or matched way down on a rank list. I will gladly share more information on this if anyone is interested in a PM.
As far as post-merger programs, I think SJP and Carilion are good as they stand right now with Columbus, PCOM, and the NJ program being "on edge" and the rest in a group that needs to re-evaluate whether or not it's worth the trouble to enact huge changes to remain in compliance.
The ACGME requires a program to have myriad other programs if they want to have neurosurgery such as gen surg, neurology, anesthesiology, etc. Obviously only SJP and Carilion can claim these at their base hospitals as of now. This doesn't even begin to delve deeper into the neurosurgery requirements themselves such as the number of each types of procedures/cases/etc.
The merger should help the cause of DOs in the future and probably long-term in all specialties, however the short-term for DOs in neurosurgery is definitely more bleak than bright. It remains to be seen how many formerly AOA programs will continue to take residents in the coming years and if the MD programs will finally eliminate their bias (I doubt it). There are those that speculate that DOs will become the "degree of primary care" since MDs will eventually be applying to the formerly AOA programs as well. I'm not sure if I am that pessimistic.
If I had to guess, I would say that SJP, Carilion, PCOM, Columbus, and then maybe 2 out of 3 or 1 out of 3 of Bromenn, NJ, Arrowhead will survive past 2020.