For what it's worth, Blondie told me that there's no Beach Boy connection to the track other than being recorded on the group's dime. I don't recall who exactly the actual players were on the tune -- but it was no one from the BB camp.
But still I can hear Carl backing vocals very clearly on this track.
I'm with Howie - never heard any other BB on this track (unless you count Ricky), and it was first introduced to me as "a sorta Flame track".
O, I'm not doubting at all that this is what Blondie has told you, Howie. And I have no reason not to believe that Blondie is telling the truth when he mentioned it as a sole Blondie/Ricky collaboration. And listening to it, to me it doesn't sound like a Beach Boys production at all, nor that I can imagine any of the Boys playing on it.
The only reason I responded to your Blondie-quote is that it sounds like Carl singing some background voc's on the bridge.
Listening to the All This Is That b00t as I'm typing this. If you have that one, check out the "Hard Time To Live, Easier To Give" line at 1:14-1:20 and 2:11-2:17. It certainly has that CW-vibe in it...
But my ears can be fooled of course.
O, and I forgot to mention that I really like this song. And for that matter much better than the Rare Bird cover on their "Somebody's Watching" album from 1973.