I was a paramedic for 14 years in Toronto and I've seen several drivers do this.  Each time I stopped, got out of my car and told the person not to follow me.  If they got into an accident following me then I'd have to stop and help them, and the person I was responding to would have a delayed response.  I always felt that we should have a camera facing backward that the second paramedic could monitor and if someone was 'drafting' us we could just send the video of it to the cops and they'd send the dangerous driver a massive ticket.

I do have to say though, that MOST people, MOST of the time, are thoughtful and let us through.  We notice that, and we thank you.  It's a privilege to be able to help.

Also, for the record, EMT is a (mostly) American term.  In Canada we are all called paramedics.