Well, McD's gets all their stuff from third party suppliers and vendors, and as such, doesn't have total control over what exactly goes into their products. The best thing they can do to that end is be reactionary, and change suppliers if they get tainted stuff.
No, they can demand that their suppliers conform to certain standards (and make them prove it by having a third party check them), or they won't buy from them. The people selling them meat will comply because mcdonalds is such a massive market.
Yes, but that costs money. If there's one things corporations don't like, it's spending money.
The cost is really pretty negligible, it will probably come out to a cent or two per burger (since it would raise the cost of meat by a little, and even then the majority of the cost of a burger is labor).
That said, you are right, they don't want to spend the money even if it would prevent deaths.
Yeah, but even then, no inspector is perfect, and stuff will slip through the cracks as people quietly lower the quality to make more and more money for less and less effort/resources.
It's not perfect, but it would result in a lot less of (whatever they are trying to prevent), and since the producers would pay for the inspections themselves, there would actually be some guaranteed oversight compared to how much of a failure the government is in food inspection.
Yeah, it would be possible to fool them, but it would be a lot harder then it is now.