Over in PA, we have numerous Regioinal Police agencies, configured as a cost savings. There are also Regional SWAT type units. One that comes to mind is The Central Montgomery County Special Weapons and Tactics (CMSWAT).
http://www.westnorritontwp.org/index.aspx?NID=168
I worked with a guy from this unit, when it was named differently, and I knew the funding came from various sources. There were also private/ civilian donations, due to the Corporate client base in the region. The nuclear plant had some donations, as well.
From an LEO stand point, the chain of command went through the SWAT organization, when called into formation/ duty.
The only thing I can think of as a "corporation" basis, is along the lines of Volunterr Fire Companies. I know many of the VFCs do fund raising, but a large portion comes form the municipalities they service. This opens up the entire Municipal/ County/ State/ Federal funding and grant game.
I always love to see the VFC Chief driving his vehicle hundreds of miles on personal shopping trips with his wife. Yeah, so he can be ready to respond. Sure.
Massachusettes is a Commonwealth, like Pennsylvania, so maybe there is different laws/ rulings as to the formation of the LE Agencies.
The National Tactical Officers Association has a web site and they are VERY active.
http://ntoa.org/site/
Something similair in NY and NJ is the Port Authority of NY/NJ. They are a Corporation, though they have a huge police presence. Their LEOs are certified in NY and NJ. Trying to get information from them is nearly impossible.