I've put a lot of thoughts into these non-combat (utility buildables) and I have decided I don't think they should share the same BP pool as turrets and the like. Why build a crate or a tree at the expense of real defenses? Sure in UBP this is fine, but in regular games, I see no reason to build a crate except in very special circumstances. What if instead of using BP, we just give each of these buildables a finite limit to how much of each you can build. (eg 3 crates, 1 tree, x# of bridges, etc)
There's a reason why crates cost 1BP and give almost no score, as opposed to a tesla generator. It's easier to code how it is, and a simpler GUI.
Plus, players should be able to build whatever they can when they want...if the situation requires. This also teaches good building habits. 
I'll try to make my point by using an example.
By default, both teams have 100 bp. For humans, thats 2 nodes, an arm, a medistation, and 7 turrets with 6 BP left over.
A repeater costs 4 BP, so if ever want a forward, that only leaves 2 BP left over. This would be the only reason I would ever build any of these "utility" buildings. Any more than two and I'll have to give up actual base defenses, which doesn't make sense to me. You might be thinking 'Well gee Prophet, more turrets doesn't necessarily mean better.' While this is sometimes very true, at least the aliens have to take the time to destroy that extra turret, where as they would simply hop over a bunch of crates or something.
Even in UBP CZ server, we see that most of these utility structures go unused (With the exception of the tree, it makes a great super barricade and grass also is very much a worthy structure hide shit even if no one actually does it) But for the most part, people would rather just stack turrets on top of each other than even worry about crates, bridges and the like. I go most games without seeing a single "useless" structure in UBP.
If we put these structures on a numeral limit to each instead of a BP value, it will encourage builders to actually use them effectively. For example, if know I can only build 2 crates (Maybe 3 at S2 then 4 at S3 or something like that) I will use the 2 crates I have accordingly to improve turret positioning as much as possible without actually sacrificing the BP to defend the base.
Finally, it makes sense: Why should a crate use power??? I don't see people at storage houses plugging in crates to the wall or something, that doesn't make any sense. -.-
