You seriously think anything at Foxconn production-wise happens without Apple's express clearance? Dream on. The color of the protective gloves the workers wear most likely had to be cleared by Tim Cook first.
As for your other questions, yes, that's exactly what companies are supposed to do. That's why they have legal research teams on their payroll. Though its highly unlikely they'll find all patents which their product may infringe upon. In most cases, the company who's patents are in question will go to the infringing company, and ask for a licensing fee. I say "most companies" because Apple NEVER licenses anything, whether they are actively using said patent or not. They are quite simply that greedy kid in class that hogs all the good toys and doesn't share. BU most likely did this, and Apple gave them the business version of "go piss up a rope," and hence we have a lawsuit.
Do I feel bad for Apple? Not in the slightest, because expensive litigation is exactly what a company that patents a wedge shape deserves. Furthermore, I'm astonished at any post that directs ill will at BU for doing exactly what Apple would do and has done over and over again in recent years in regards to protecting their patents. This is the business environment Apple chose to live in and has done it's best to foster for many years through similar patent litigation. Why should anyone be up in arms about that now simply because what they hath wrought has come back to bite them?
You forgot the /S or ¡