I don't know of any existing policy but most multiplayer games don't allow scripting. That being said, RTS games like Starcraft 2 have a feature where you can right click abilities to make them activate automatically, so maybe this could lead to an interesting feature suggestion.
As it stands, most players add these buildings to groups and manage them with hotkeys. Say healing gardens A is in group 5 and healing gardens B is in group 6. You can press 5 > Z (or whatever the ability hotkey is) to activate it. When the effect wears off then you click 6 > Z and so on. It's not too cu