Requiring folks to carry an extinguisher is stupid and does nothing for my safety. The only reason I need a system is if I'm trapped/incapacitated in the car and it is on fire. In that instance, the chances of being able to use the bottle are almost nil. If the car is on fire, I'm out of it.
On the otherhand, requiring extinguisher systems makes sense.
BTW - the GCR as written does not require or allow the use of either in an IT car. IIDSYCorMTYC.