Do tyranid spores come down automatically turn 1? I thought they were normal reserves. If not, then you're screwed because you'll lose turn 1 and nothing is on the board. If they come on turn 1, then great, tyranids can do it too.
It doesn't specify in the BRB or the FAQ however if they do or do not count as area terrain. All it says is area terrain needs to have a clearly defined border (which battlements do) and area terrain is difficult terrain (which battlements are) so if it looks like a duck and quacks like a duck... Seems i need to do some more interwebz searching on this one.
No. Things are area terrain for specific reasons. One of those reasons can be "because both players agree to call it that" but that's something that's based upon the terrain modeled. i.e., it's a pile of rubble, or a swampy type thing, or a pile of alien cotton candy, or whatever.
SOme things are always area terrain. Forests are, wrecks are, craters are.
Ruins aren't even area terrain (the bases are often considered such) though they are difficult terrain (presumably cuz there's broken masonry scattered everywhere).
A building is much like a ruin before it got ruined. There's NOT stuff scattered everywhere. It's worth noting area terrain is ALWAYS difficult terrain. Why would a race make it hard to get across their nice, smooth, battlements?
Battlements aren't area terrain because they don't share any of the features of area terrain. I WOULD think it reasonable to have the same +2 if you go ground rule that the Aegis line does, cuz they're constructed like crenulations, and I mean, look at it, it's just like an Aegis line, but on top of a building.
But they don't share those rules, so there you are. Truth is the Fortification rules are awful, contradictory, and not thought out very well. More than usual, I mean.