Based on traffic
calls, the two of them are between 500 and 800 feet. They're basicly
parked right in the final approach course to the active runway.

If necessary PD can give LGA a "Priority"and the Tower will actually stop or
delay departures and arrivals. But PD will only do this in extreme cases. For
the most part they will low level and the tower will call off the
departures/arrivals. They work very well together to minimize any problems.
BTW, helicopters use the 126.050 frequency at LGA not the tower 118.7.