Bytrol is indeed a 'carrier' for antimicrobial compounds. But eventually, microbes develop resistance to most antibiotics (just like with MRSA), which renders these compounds useless. However, Bytrol's ace up the sleeve is it's primary mode of action: stopping microbes actually adhering to surfaces in the first place, making it very hard for them to grow. Byotrol uses biocidal action as a secondary form of defence - it's the physical barrier of stopping adherence in the first instance that is key here.
PS. I see BYOT is blue again today. Unfortunately I have still not bought, for two reasons. 1) taking a real pounding in TMC at the moment, but am determined to hold on; 2) feel that BYOT may fall back a little over the next couple of months until further news in announced. (But only IM very HO... I believe interims are due soon, maybe they'll contain some pleasant surprises?)