When the B.F.Goodrich Radial TA's were introduced in the early 70's, they would "True" every tire they mounted. They used a spinning round "knife" and as they spun the tire on the balance machine it would go back and forth across the tread removing the high spots like it was on a lathe.
I remember seeing a good amount of rubber piling up on the floor, and I told the tech I didn't appreciate seeing the 4 tires I just paid over $100 for being striped of so much of their tread.
He promised me they would go a lot further being perfectly round than they would being out-of-round.
I had them on the car for nearly 15 years, as a matter of fact, I kept them when I purchased new tires. They still have a "useable" tread depth, and no cracking. The rubber is a little "hard" though.
I don't know if they still use that procedure or not. You might be able to find out just by calling different tire stores in your area.