It has always surprised me how some people try to identify the earliest point at which they can “safely” remove their headdress in any location or event. It would be impracticable for the Dress Regulations to list every single possibility for absolute clarity; common sense, awareness of custom and tradition, and awareness of chain-of-command expectations remain a necessity. Some of those are picked up through specific instruction, some by following the examples of those around you, and still others by trial and error. Erring on the side of caution is seldom a poor choice.
Based on my own opinion (fully acknowledging that others may approach things differently) and experience, I would offer the following:
The customs of civilians wearing or removing hats is based on the days when a gentleman wore a hat as a matter of course, removed it only when social custom dictated, and tipped it to passing ladies. A man's hat was removed to dine (at home and in restaurants), for religious ceremonies (churches, but not synagogues where headdress is customarily worn), and in court. Hats were kept on during normal transactions of business with others, in and out of doors, and were generally part of a man's attire when there wasn't cause to do otherwise. There were, of course, removed in relaxed circumstances, at home or in one's own office or workplace. The traditional rules on hats were not based on modern habits with wannabee-gangster-punks wearing baseball caps backwards, or the habit of stripping a toque from one's head as soon as you get into a warm space.
Some enclosed spaces may be treated the same as an equivalent outdoor space. For example, many armouries have expectations that the drill floor will be treated as a parade square and headdress will normally be worn on and about the floor. The wide open spaces of a mall or airport may be considered similarly and headdress worn, even though the Dress Regulations are not specific about it. When in such an area, if entering a dining establishment, etc., revert to the observations above.
Some, perhaps, seek that first opportunity to remove headdress in order to avoid having to salute. It's a poor reason because it doesn't excuse the expectation to pay compliments by other actions. There are even some areas where the removal of headdress to minimize the perceived disruption by continual saluting within a “captive” group of service members has been made the norm: the concourses of NDHQ and the interior of Fort Frontenac in Kingston come to mind as examples.
The wearing of a toque when the weather is cold enough has become the expected norm. It does not, however, completely excuse the individual from considering if a different headdress might be more appropriate at some time during their day. Wearing a toque because you'll be outside for most of the day doesn't make it improper to be wearing it for a short visit to the BOR or another indoor space. Choosing to make it your daily headdress because it's winter and you don't feel like carrying a second hat may not be the best choice if you have to meet members of the public, or report to a senior officer's office wearing it. Just as the Dress Regulations can't predict every possible place you might have to figure out what hat to wear, it can neither describe every possible workplace circumstance.
All I, or anyone here, can suggest is: be aware of the Dress Regulations, be aware of any local expectations, and be prepared to justify your own decisions. To be prepared for the unexpected, carrying an extra soft cap, or having a spare at your workspace, is not an onerous task.