This was all considered pretty illegal when they first came out because _cz maps were meant to be played with CS:CZ. These days I'm not sure if it's the same. Anyway, CS and CS:CZ are basically the same game, so I assume the maps would be cross compatible.
I understand what they were meant for but most map sites now carry these maps under the 1.6 section of their site. Those are the ones I have. I have CZ also so I was checking out what other maps they have available and it made me think that it would be cool if the CZ maps that are listed only in the CZ section of the websites could also work for 1.6.
I am sure they would rather you play the CZ maps on a CZ server but at least you are giving people that have never played CZ a chance to see what CZ has to offer.
I know when CZ first came out, there were some packs floating around that were considered illegal but the maps I have were advertised as 1.6 version of the cz maps. So if it was illegal, you would think the places that are hosting the maps would have been hit with a lawsuit. Example http://www.fpsbanana.com/
has cz maps listed under 1.6 and CZ.
I apology if I brought up a controversial topic.
Thanks for the reply!