It is available on one of the computer screens that the police access when doing a query on a person. Thus it is available to anyone in law enforcement.
It is "supposed to be kept confidential", however I know of one chief who released the list of all LTC holders to opposing counsel (illegal act) in a court case against the chief for failure to issue a LTC (court upheld "chief's discretion" although person involved was spotless and a "townie").
Since the MA RMV allows insurance companies to have their people "sit" in the RMV offices and allows access to their driver database, I am unsure (and untrusting) if these folks can access LTC info (it is all an inter-operable computer system, but restrictions can be set in place if they want to do it). Since the insurance folks sell/give client (medical and credit at least) info to large national databases, again I am totally non-trusting . . . but there is nothing we as mere citizens can do about it.
A side note: I would NOT trust the MA Criminal History Systems Board (aka Firearms Review Board) in keeping any info confidential! Likewise in a Chicago against gun mfrs case, a judge allowed the City of Chicago to get info on all gun purchases and purchasers (I guess from 4473 ATF forms) anywhere in the US! Memory on this is a bit fuzzy, so I don't recall the details.