Crimson EMS now has 63 EMTs

https://news.harvard.edu/gazette/story/2019/05/crimson-ems-trains-harvard-students-in-cpr-and-other-life-saving-techniques/

Harvard University - Cambridge Mass

Pro EMS is a private ambulance company that works in conjunction with
Cambridge FD to provide EMS in Cambridge - Cambridge FD has multi
medics and EMTs - plus 2 medic vans - and Pro EMS provides staffed ALS
and BLS ambulances

MIT has their own student staffed BLS ambulance

I have never heard Arlington FD Rescue going to calls in Cambridge -
but there have been a few times when Cambridge Squad 4 and Pro EMS
have come to calls in Arlington

And - there are multi private ambulance companies in the Boston area
that will show up in Cambridge at various times - in fact Spaulding
Rehab Hosp Amb Service might be garaged in Cambridge