fruitbatflyer,
I'm suprised your company set missed approach heading on the MCP of the BAe 146/RJ. As you know, things get quite interesting in the simulator when you have an engine failure on the go-around followed by a turn if the autopilot is engaged - all due to the parallel rudder.
This isn't an issue with the ATR or B737 so maybe this was done to standardise fleet SOPs.