I think some units are using soldiers' "Family care plan" as an excuse for their own poor planning. As a supervisor, here is an example; I call someone at 2000hrs because a morning timing has been moved up 2hrs or because I need an HLVW driver for a last minute 0500hrs task and they said "Warrant, I can't drop the kids off at daycare before 0700hrs and the babysitter that is my "family care plan" is away this week." I respond with, no problem, I will find someone else this time.
Like it or not, family dynamics have changed. There is no pool of soldiers having a beer on the couch in the PMQs ready to go at a moments notice because their homemaker wives are there to look after the kids. The wives work too now, and have jobs that are even less flexible than ours, or she is in the CAF as well, and her supervisor expects to come first occasionally as well.
When a unit takes over IRU, and soldiers are going over their kit in the unit lines making sure it is good to go, they then go home and do their best to verify a working emergency family care plan is in place but this isnt easy, and is rarely a permanent arrangement.
Fanouts, bug outs, quick trains, etc. are an exercise of the system to see who and how many you can get on short notice. This is a study for the planning process. It is unrealistic to think you will get everyone in.
Any CO I've had in recent memory put the working hours in the Standing Orders and reserved the ability to bring soldiers in early at his level or perhaps delegated to Coy OC level.