According to the Massachusetts Division of Insurance (DOI) if you are determined at fault in the accident for an accident, you are sent a Surcharge Notice. It appears that you took action by appealing the surcharge notice with the Board of Appeals at the DOI.
Since you disagreed with your insurer's surcharge determination and believed you were 50% or less at fault for the accident, you had a hearing regarding the incident and apparently won. So according to the DOI site if you win the appeal, you will receive a refund or credit from your insurer for any excess premium you have paid due to the surcharge.
The DOI does not mention if you will be reimbursed for expenses due to how the claim was originally processed by your insurance company. Nor does it say that the insurance company must reverse their decision regarding fault, it states only that the insurance surcharge points will not be placed on your driving record now.
You will need to contact your insurer to find out how winning the appeal of the surcharge now affects the original claim. It might be that your insurance company can now subrogate with the other party's insurance to be reimbursed for the monies they paid out. If so you might be reimbursed for your deductible and rental car expenses.
If appealing the surcharge does not change how your claim was originally placed you may not be able to receive back money. Beyond checking with your insurance agent on this matter you can also contact the Consumer Services of the Massachusetts Division of Insurance for information.