I don't have any 24-70 mm f/2.8 lens. But I do have the EF 24-105 mm f/4L IS II USM, and had the EF 24-105 mm f/4L IS USM before that. For these two, the lens hood designed for the EF-S 17-55 mm f/2.8L IS USM fits fine. No vignetting on full format, but quite a bit better protection of the front lens than with the hood that accompanies the two 24-105 lenses.
The design of the EF 24-70 f/2.8L USM is quite unusual. Almost all other lenses get longer when set to longer focal lengths. So does the EF 24-70 mm f/2.8L II USM. But the fact that the first version works in the opposite way, combined with that the hood is sitting on a part of the lens which does not move during zoom operation, means a much larger hood can be used. Note that the total length of that lens, with the hood included, doesn't change during zooming.