Well in our BLS+ system essentially we treat on scene within reason.
For example, severe SOB pt. We would do primary, O2, vitals and start a ventolin treatment on scene. Our protocols state we should initiate transport after the first dose of ventolin with further treatments given enroute.
12 leads done on scene as long as they don't increase on-scene time more than 2 minutes.
IV initiation should not delay initiation of transport
Most of our med protocols involve at least the initial dose started on scene (ie where the pt is found)