UPDATE: This fix is now incorporated in morroblivion-fixes-v1_5. You don't need to download this fix if you are using that mod. You also don't need this fix if you don't use MorroblivionTreeReplacer.
Here is a quick fix to the Ghostgate issue requiring TCL to go through the barrier between the gates.
I've adjusted the collision blocks so that you do not have to resort to console commands anymore. The issue turns out to be an old dirty record in "Morrowind_ob - MorroblivionTreeReplacer.esp". If you use that plugin, you will need this fix.
Issues/To do: The barrier is still visually present between the two gates. This may require editing the NIF model to make a hole. Fortunately, that section of the barrier is only used once -- so making a hole in the model will not result in holes anywhere else in the game. FYI, There is actually one ITM record in the esp -- this points to the section of barrier still causing the visual issue.
Load order should be after Morrowind_ob.esm but before any map replacers. Load order should be after "Morrowind_ob - MorroblivionTreeReplacer.esp" and before any map replacers. If you're not using the MorroblivionTreeReplacer, then you probably don't need this fix. (FYI, fix will be incorporated into morroblivion-fixes-v1_5.esp)