So since you asked to post my feedback here, here you go
------Overall------
-I think this stage has the basis of being pretty solid, though needs some changing to get there
-I like the theme you're going for, I'm a bit of a sucker for anything set in TF2's standard setting and it's not often I get to see anything set in a trainyard like this especially set on (presumably) a mountain side
-Both points have a bit of an issue of being easily rolled since RED about half the time doesn't have time to set up from their previous defense.
.-Funnily enough I noticed a bit of a pattern where RED would commit to holding the area infront of BLU spawn, get wiped because they committed to holding the area infront of BLU spawn (which in fairness, is a decently defendable area in isolation), lose A since what remaining survivors can't hold it due to being out numbered, and then if BLU gets enough respawners in the forward spawn and RED doesn't get enough respawners to set up second gets rolled.
------Hard to Hold------
-This is prob the biggest thing I have to say on the matter so here you go
-When defending, it seems that both points only have a backward hold to them, meaning that if RED fucks up once they lose the point.
.-This is bad because it can be frustrating for RED to hold and generally anticlimactic for BLU to take
-Typically, you want to have a forward and backward hold for RED on A/D and Payload so RED isn't punished for making a single mistake while not being too frustrating/exhausting for BLU to take
-For second however,
------Second Point------
-Second is very interestingly balanced, It's essentially just one large choke with cover designed to have most of the combat happen across the train tracks.
-here's what the the current front line look like
-BLU has highground on the top but is generally dangerous to use since it leaves you vulnerable to spam. Still an important area to try to make an opening to attack the point from
-the bottom route puts you on low ground but is relatively easier to attack from since it's relatively more difficult for RED to defend
-RED had to defend the point from a single choke that's surprising to too hard to hold. In order for BLU to push the point they essentially have to flush RED out of their choke to cap. One it reaches this stage BLU pretty much wins.
-RED can try to hold infront of of the point but is generally pretty risky due to low ground and a difficulty retreating
-since this is the first stage on a three stage map you should make sure it's not too easy to defend
-Also you prob know this already but the retractable platforms spanning the rail line when active make it easier to attack. Nothing wrong with that I just think it's neat
----- The area infront of BLU spawn ------
-This area seems pretty unfocused and is ironically easier to hold than A at times
-The design of this area doesn't matter too much as long as BLU can easily overrun it and RED can retreat to their forward hold on the first point, lest this area is meant to the forward hold (which it's not with how it's set up)
-Quite frankly I'd just redo this area. It's complicated, awkward, narrow, and is a solid defensive sniper sightline
-The distance from BLU spawn to the first point is good so don't change that, though this area and first could be resized a bit
-I would recommend you try to what this area's function is in the game word as an actual place rather than just a gameplay space and then try to turn that into a gameplay space since this area seems pretty confused as to what it's identity is. Of course, gameplay is more important than detailing but I think it'd help give a bit of direction to make this area.
------First Point------
-RED, assuming they didn't get wiped trying to hold the area out side of BLU spawn, they have to play on their backfoot to hold first which can make it a bit frustrating. However, the literal hold itself is fine
-Here's what the front line on first looks like (when RED gets to set up)
-I don't really have much to say about A since it's generally pretty good, just need a bit of tweaking as to push BLU's initial front line further away from the point. This would fine if BLU forced RED to retreat to it from a more aggressive defense
-----Misc-----
-Some of the transitional area can be confusing to navigate, though it seems like you've been bettering those already
But yeah, that's about what I think on the matter
Best of luck on the contest