In regards to Mass. considering more involvement of their state police in enforcing immigration law, there are lots of caveats and lessons to be learned from looking at how Arizona's state immigration laws are being used.

http://www.eastvalleytribune.com/page/reasonabl…

It is a big issue of state versus federal laws. In the series linked above, there are many examples of how Joe Arpaio of Maricopa County, AZ has patently abused the law and stomped on the rights of everyone, citizen, legal residents and undocumented immigrants. One of the most horrifying abuses is detailed in the first installment, where a deputy makes a traffic stop without probable cause and jokes how they can “make it up later”. So far there has not been a challenge to the legality of Arizona's law but it will be coming.