I can confirm that side mounted MP turrets worked about a month ago (that is, before I started playing Age of Pirates 2

). I didn't checked since then, but judging from Nightly logs, this code wasn't really touched recently, so there's no reason why they shouldn't be working.
On the other hand, they can be tricky to set up, so Spoon could have been complaining about it not working, because he did something wrong when setting them up (and stopped reporting about it once he found and fixed the problem, since both Challengers in WoD work well). The only problem I had was with rear-mounted MP turrets (on Scooby's fighters), but I have a few theories that I'm going to check before bothering SCP about this (though I don't know when I will do that, due to aforementioned AoP2).