Was hit by a snow plow, What kind of a case do I have against other driver's insurance

Probably, somewhere in the range you've already indicated, i.e., around 50-50.

Do not rely on the insurer; get an attorney.

The insurance company is probably about right, that being said, all that you have to prove in Massachusetts to succeed in a personal injury claim is that it is more likely then not that it is the plow drivers fault. You should consider consulting an attorney.

A better than 50/50 case. The plow driver had the obligation to yield meaning you had the right of way. Much will depend on the points of contact between the vehicles as well as any other physical evidence.

I am guessing that you were not injured in the accident, or you would have sought representation. I say this because if you have a property damage claim, only, it probably is not worth getting a lawyer involved. If you had a lawyer, and if the insurer is now claiming it is a 50-50 claim on fault, then an effective advocate could probably get the insurer to accept greater responsibility. Unfortunately, you will have a difficult time getting a lawyer involved in a property damage claim. If you have any injuries, and if your medical bills exceed $2,000, you should call one of the fine attorneys on this list.