I found a way how to complete this map without the Blue Keycard.
I made a video: https://www.youtube.com/watch?v=V8DWE4g9G58

This map is supposed to work in conjuction with Nuke City 1 and there is no way to do that so it pretty much ruins the experience. So downloading through workshop and playing just isn't worth it. Do yourself a favor and just stick with Nuke City 1 and don't bother with this one unless you can play them together as you're supposed to.

Yes, it doesn't seem to use the custom con or art files. It's a pity, because they make a huge difference on this map.

So, yeah, it doesn't work probably.

IIRC weren't you supposed to get one of the keycard by killing the boss in the original map? I'm pretty sure it was the case and it involved custom .con file, which can't be done on Steam workshop. I just tried the map and I couldn't find any keycard so I don't think the map works as it was meant to, I don't think it's compatible with the workshop unless you modify it heavily.

Kind of a shame beacuse it's a really great map, solid and detail with a great layout and rooftop fights.