Slitherine

The FAQ for buildings says that troops in column may only enter or leave from a point where a road touches the building, but doesn't say whether they are able to occupy it. (they cannot immediately defend it)
The next section says that infantry entering a building to occupy it must be placed in Tactical formation even if normally allowed only skirmish formation.
So this would imply a free formation change??
Does this mean an infantry unit that enters a building along a road in column to occupy it is than immediately placed in Tactical formation?

I think my head is about to explode!

Yes if you are in a column and move into a building you automatically assume tactical and are occupying.
Likewise if you are in a building and want to leave you can move from occupying to leaving in a column on the road. Sometimes easier to get out than trying to pass a CMT and constantly failing, been there...