Only when I click on the app icon in the dock does it come to the front. Option "All WIndows" or "Desktop on Display 2" doesn't matter, app window does not pop up.
In Sys Prefs, I unchecked "When switching to an application, switch to a Space with open windows for the application."
→ this allowed BusyCal to appear on display 2 !
(This was not necessary to do for the macro for Safari, TextEdit … to work.)
tell application "System Events"
tell application process "Dock"
tell list 1
tell (first UI element whose name is "Mail")
perform action "AXPress"
end tell
end tell
end tell
end tell