My father's property is about 3 acres of lawn with multiple trees. He uses a backpack blower to blow the leaves into rows, then tows a big vacuum unit with his tractor down the rows. The impeller on the vacuum unit grinds up the leaves, small branches, and unwary rodents.
I'm guessing this is what you meant by "yard vac"...
His vacuum is a more industrial sized version of this thing.
And his tractor is a tractor - not a "lawn tractor".