"blue up" l think your info is a little suspect on the tie bolts.
The tyre changer as you put is contracted out to one of the tyre manufactures l believe, as it is at a lot of airlines these days due to cost.
If you replaced the tie bolts at every cover change it would cost hundreds of thousands of pounds, dollars or euro's a year per fleet.
However a lot of airlines are looking into the problems of tie bolt failures that have increased all over the world, with help from Boeing and the wheel manufactures.