What is the point of destroying okw base ? They will for sure have all tiers in the middle of the map.And you can't do base rush on maps like rails and metal.
The point is you always know where his starting location will be. Therefore you can easily destroy one truck and deny any new units from that building. If it's a 2v2 and one player is Ost, then you can cripple one player outright.
The point is fighting asymmetrically because if the OKW player has good support for their KT and knows what they're doing then you WILL NOT WIN facing it head on. Your advantage is being able to switch between sides of the map faster than your opponent.
Does it work every time? No. It needs a lot of good timing, micro, scouting, and some luck. Plus, as you said, maps do make a difference. Sometimes it's a nogo strategy. But always think about ways to just avoid your opponents super-heavy tanks. An OKW player wants nothing more than you trying to rush your precious jacksons and m-10s into a line of vetted volks with shreks, pumas, and a KT.
Now, what about the rest of the OKW base? It's in the middle of the map. Usually they don't clump them all together though. Pick the isolated one and go after it. Artillery is especially useful here. Honestly though, if your opponent has a well dug in base in the middle of the map and a KT on the field with good support, you may have already lost.
Also, a question. Does anyone know what the spawn time for OKW command trucks is?