Boston EMS does not have any police powers. If we restrain a patient w/hard restraints they are transitioned to soft restraints if possible w/o risk to patient or crew. Batons, Mace, Tasers, etc...are NOT allowed, and if I saw someone with any of the above we'd have a talk. I'm sure there are people who conceal self defense items on their person however they are not authorized by any policy.
As far as BPD using EMS to restrain people, yes and no. If it is a patient, i.e. psych illness, intoxicated party in need of MEDICAL care, then yes, EMS is actively involved in the restraint, ideally w/police assistance.