If the fire starts in a bedroom, its behind a 30min s/c FD and the HD/sprinkler head in the bedroom will not only raise the alarm but extinguish, or at least control, the fire should it take hold and grow. HDs in bedrooms are to raise the alarm incase cold smoke/pyrolysis products are not buoyant enough to activate the optical SDs in the corridor. Let's not go into the argument of alerting the person in the room of origin.
As the corridor is a protected zone, there should not be any combustible storage/obstructions. But assuming sods law and a fire does take hold in the corridor, the optical SDs should raise the alarm before the sprinklers go off - giving early warning (as would be the case in a non-sprinklered building) - but here's the difference: the sprinklers should either extinguisher or limit fire growth in the corridor. The smaller the fire - the less smoke will be produced and so the longer it will take for the smoke layer to descend to head height and threaten egress. Therefore, the need for doors for smoke control purposes may not be as vital....I take the point re. keeping the storey exits separated and thus "containing the fire" to a smaller compartment but some would argue that sprinklers do the same job.
Sure, cross corridor doors might increase the level of safety a bit...but then where do you stop: there is always more that can be done. In other words, are the benefits justified by the time, cost, expense etc i.e. is it reasonable to ask someone to fit corridor doors when they have a sprinkler system.
I've not totally made up my mind on this and, to some extent, I'm playing Devil's Advocate - hence why I'm interested in views.