[Lizard]

[Yup. That's pretty much exactly what I did. Sorry all.]

Here's a super-quick copy/paste script that just handles task names. Would it be useful if it copied any other properties too?

set names to {}
tell application "OmniFocus"
	tell content of front window
		repeat with t in selected trees
			set names to names & name of t
		end repeat
	end tell
end tell

names

tell application "OmniPlan"
	tell child task 1 of front document
		repeat with n in names
			set foo to make new task
			set name of foo to n
		end repeat
	end tell
end tell

Select some tasks in Focus, run the script (you can stick it in the OmniFocus toolbar if you like), and the tasks will be added to your open Plan document.

EDIT: Yes, I realize it would be better if we just added sensible copy/paste support, and I've added your comments to that bug. But I thought this workaround might be helpful in the meantime.