Short Answer - Most Likely Yes
Well, the Cadillac and Chevy interchange, and I can't imagine Buick altering their fitment from the other models for no good reason. So, while I have not done it myself I'm going to deduce YES.
The real reason for my post is to ask why. The FWB front and rear bars were quite flimsy compared to the SS bars I replaced them with. And for reference, I run double SS bars on the rear.
Only in the event that your RM currently has NO bars and you have the Fleetwood parts free then you'll see a little improvement I guess. I'd personally hold out at least for a set of old SS bars for legitimate handling improvements.
Plus, if going to the trouble to remove rear LCAs then I would never replace them with more OEM units. Definitely a call for aftermarket upgrade there.
\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!