I don’t know for sure, but I do know someone to ask. I think it depends on what types of plastics your city recycles. At first our town only took 1 and 2, but upped it to 1–6 after that. I do know that the cap is a different type of plastic than the bottle itself, which is why you have to separate them. If you look inside some plastic caps, they are also duel layer, and that may well be the reason that you can’t recycle them at this point, since they are fused together. The single layer ones aren’t marked, so there is no way to tell by just looking at them, but some of them seem like they’d go in the mix, at least here. We have a bin for mixed paper, another for yard waste (which includes soiled pizza boxes) and yet another for all the other mixed stuff, milk cartons (both types, cans, most glass and accepted plastics. Cans have to have labels removed because of the way that they are processed.
Thanks for asking this, lefteh, I was wondering the same thing. I’ll call and find out the local answer and then ask the friend that I know who is in the business and see if I can find anything else.