Hi Amy,
Right now, due to budget cuts, we are not on call officially, but the
pathologists all have a list with techs' names and telephone numbers. We
amongst ourselves rotate so that once called in, you fall to the end of
the list. When called in we get paid minimum for 2.5 hours, at the rate
of time and half.
We used to have scheduled on call list for the weekends, which meant
that the tech on call had to be reachable ( we had a pager) within
determined time and get hourly pay for that time (@ $2-3/hour).
The way we are doing it now, may potentially  leave the pathologist
without a tech, but so far it has worked OK.
Katri

Katri Tuomala
Anatomic Pathology
St.Joseph's Hospital
Hamilton, Ontario, Canada