I’m not so sure you have to tell them anything, just pony up. I’m fortunate to be in a shop that had 3-phase before I bought it. When I upped the power from 200-amp service to 600-amp service the GaPower engineer did mention the possibility of charging me for the upgrade. Thankfully the pole and transformers are on the sidewalk maybe 25’ from the meter base. They waived the charge as the transformers were slated to be replaced anyway. I guess they weren’t super worried about 100’ or so of wire, since they already had a crew scheduled.
All that said, one thing I did have to do was submit my load requirements. Basically I just took pictures of every motor plate in the building. Not that 1/3 of the tools would ever be turning at the same time, but I inundated the engineers office with close to 3000 amps of potential. After GaPower agreed that I was selling myself short on incoming power I turned the rest over to a licensed electrician to do the rest. Like most utilities, you own everything from the meter-base on and the utility owns the rest.
I’m guessing you’ll have to do similar and pay for the cable runs. But, from my experience, I would be prepared to furnish the power company with a reason. Also from my experience, they don’t verify anything you submit to them, so take pictures of every machine you’ve already got and maybe a few of your friends machines.
Jeremy