As per how the rule is stated in the motd, "5.5 Bases If the circle breaches into a world building you may not build within that building."
as long as you don't build in them, then there is nothing written about being inside of buildings during turf if the turf reaches into them, so to my knowledge it should be just fine.
Though rule 5.2 Distance You may not attack into a turf war from an unreasonable distance/roof tops/buildings E.G if there is a turf war on the grass island you may not snipe from the sand island. states you may not shoot from buildings, though that most likely is meant for buildings that aren't inside the turf circle, so if you were to shoot from the red areas during turf that would most likely count as 5.2 but from green area it would be valid.
Nvm.
Also all buildings that go inside of turf zone have their doors so you can't buy them already.