Hodgdon has changed at least one powder between the two brand names that I know of. I have a jar of Trail Boss with "IMR" on it and one with "Hodgdon" on it. Identical other than the name above the picture being different. Wouldn't surprise me too much if they changed some others too. IMR is owned by Hodgdon of course but I don't know if all IMR powders are made in Quebec or not. Maybe they changed the name because they changed where it was made?
Either way there is only one "700-X" powder. It's not like many rifle powders where there is an IMR and H version with the same number.
*edit*
Checked the Hodgdon website (marketing site, not load data) and indeed 700-X and 800-X are now under the "Hodgdon" label instead of "IMR". I have a jar of IMR 800-X beside me just to make sure I'm still sane and the Hodgdon site is showing the same jar but with the Hodgdon logo and name at the top instead of the classic IMR logo.
The IMR website likewise no longer shows 700-X or 800-X and in fact only shows 2 shotgun powders period; SR 7625 and SR 4756, both discontinued but still listed.
I would guess that it's the same stuff since the brand name wasn't part of the powder name like it is with the rifle powders. It didn't change from "IMR700-X" to "H700-X" or anything like that. If they did move production (a guess, nothing more) then it could be slightly different? Many powders have changed over time without changing name so it's not unprecedented.
You could contact Hodgdon and ask if it's the same stuff or not. I don't know how good they are at getting back to people or answering the phone with a human being.
*edit 2*
A quick Google search turned up a bunch of rumours. One was that after Hodgdon bought IMR they had to turn back a lot of 700-X bulk shipments (made in Canada, packaged in USA) because they didn't meet Hodgdon's standards. The new packages are reported as saying "Made in USA" with no mention of Canada. So I guess they did move production? Lots of trap and skeet shooters are worried that the burn rate wont be the same and their loads will be all screwed up. Can't find anything concrete like a company statement.
Another rumour is that Hodgdon was having Alliant make 700-X for them while they setup to start production themselves in the US. So that would mean three different plants producing 700-X.
Again, these are rumours from US forums, not facts with supporting evidence.
Several people are saying their velocities and patterns with trap and skeet loads haven't changed since the powder label changed so I would guess it's very close if not an exact copy of the old IMR 700-X.