The practice of landing the outer, departing the inner is much preferred to the other way since the controller has control of when to roll the departure with reference to the crossing traffic (assuming everyone does as they're supposed to) as opposed to crossing a stream of arrivals with every departure, many of which will be heavily laden. We use simultaneous IFR approaches as our runways are about 2 miles apart.
At YYZ we too require all arrivals to remain with tower for the crossing of the inner runway. Occasionally some will call ground in between and be "educated." Some controllers have adopted a "stay with me" phrase but we shouldn't have too, it just adds to the assumption that unless your told to "stay with me" its OK to change.
Unless you're given a frequency change, don't change.