This is nice, but sadly poorly balanced. A lot of the tiles aren't very useful, and the optimal strat is extremely static and ridiculously powerful.
Namely, you want to build a network where hostile packets go through as many turrets as possible, and then use STK.TRASH to get rid of everything except: 1x RSTR.BKP, 2x UPGRD.DEF, 1x STK.TRASH (since you can't get rid of it)
This way, you are guaranteed to be able to restore all turrets from backup every turn, as well as upgrade 4 times per turn on which you do not use RSTR.BKP, or an average of 3 if you do, which with turrets decaying over 3 turns, means you can keep 4-5 tiles upgraded at ALL times - and if they're tiles with 4 turrets on them - nice.
There also seems to be three bugs that I can tell: Lategame(wave 70+), only virus packets spawn, they seem to spawn mostly on the left(unless it spawns more in lanes with more turrets?), and turrets on the rightmost edge of the map do not get repaired by RSTR.BKP.
Ex. typical lategame wave(all in leftmost lane were killed, there is never any in rightmost):