Unlike most PL maps, which only have a cart to escort, here you have a real train that you can ride on, which consists of 3 parts.
BLU must use the said train to infiltrate the RED's base. RED must defend their base from the BLU's train.
Since the train consists of 3 parts, to "block" the train, a RED player needs to stand in the same part of the train as where the BLU player stands. If there are any BLU players in other parts of the train, it will still move.
The map itself is pretty big with industrial theme, consisting mostly of large outside areas, except for the team spawn rooms. The track consists of 3 control points, including the final one.
Also, the train HUD is glitchy and may sometimes give wrong info. This is because of engine errors.
As for the map, I really like the idea, however its execution is far from good. I'm guessing this is one of your first Source releases, as there's plenty of leftover GldSrc mapping techniques used. HL2 content doesn't blend with TF2 content too well, giving the map a rather awkward look. There's also a significant lack of detail & props throughout the map. Lighting & ambience should be improved as well.
As for gameplay, I think the layout is too linear and plain, giving the defending team a fairly big advantage (engie spam?). Add more flanking routes, some camping ledges for snipers, etc.
Overall, a neat idea you should've spent more time polishing.
I agree there with the HL2 textures part, but since hammer couldn't distinguish shared HL2 textures from the TF2 ones (They all show up together) I had to put whatever I could find. Too little props? I put there as many as I could. And what about light? There is a light_environment, what else should there be?
And the design really is too linear, but since this is a pl map... ah nevermind.
Maybe, but the overall picture you know ...
More variety in colours/tones, etc.