If you're a company providing expensive computers to white collar workers, you should probably just be giving your people new machines to use while their machines are being repaired anyway. In that scenario, it doesn't really matter if repairs take longer because broken machines need to be shipped to Apple.
Not sure what you mean here.
I don't know of a company on this planet who is self repairing Macs.
We self repair macs at our university. We have staff in our dept that are authorized repair techs. I'm sure many larger organizations have a similar setup.
Authorized Service Facilities have access to the required tool.
My company buys Macs on warranty and just ships them back if there are problems.
Corporations could probably become authorized. Large entities will have the requisite scale to make it economical.