Since most jurisdictions in BC accept FT4 in plenums now, is it okay to run unskinned TECK and ACWU in a plenum ceiling, or am I missing some other rule here? thanks.

Since teck finally has FT-4 marking on it you can run it with the sheath in tact in Greater Victoria both jurisdictions. Vancouver may not permit it as I think they still require FT-6 in plenums.
There are now some fire stop products that eliminate the requirement to strip the jacket when penetrating a fire seperation but be sure the building inspector recognizes the product and its application first.