Heimerdinger turrets + Banshee's veil

Something that has me a bit confused, turrets deal magic damage but they do not proc banshee's veil. I find it a bit strange and am curious if anyone knows why? logically, it should proc it, unless the turrets do AD and not AP (which would be very weird if I do say so). Is it a bug that's never been noticed/thought about or is there any other reason for it?

Some clarity would be much appreciated ^_^