You'll have to excuse me, as I had the majority of this typed out yesterday, but was unable to finish posting. You beat me to the punch with a new version already, so feel free to disregard, but I'd still like to give some more input.
another thing you are doing at this point is this is the building that lets you start converting

Culture from various sources into

Tourism.
My proposal is to use the

City Connections to multiply

culture from tiles. So what you are doing in this time is trying to pile in

culture on tiles in 1 city to concentrate the 25%

tourism converter, and disperse that to all other cities.
Behold, in all it's glory, the megalopolis of Ottawa! In all seriousness though, I'm actually not a big fan of this because it feels like it's pushing tradition/tall/GPTI synergy when this Canadian kit favours more wide/progress/authority style.
Now, I see you've already simplified the yields by stacking for every GRH constructed, and that's more than adequate, but in regards to my last idea, what if instead of % modifiers it was just flat yields based on relative distance to closest owned city? This way, cities benefit similarly with relatively consistent yields, and you still get the unique feeling of distant 'scenic' cities (your secluded "Banff"s of the world) bringing in bigger yields. One of the main appeals of Canada's beauty is that it's so widespread, so I thematically like the feel of a bigger conversion across any/all cities, as opposed to overloading culture into a single city, a la tradition capitals / base Smithsonian -- though, being from Toronto, there's plenty of its citizens that definitively consider it the centre of the universe... I also don't understand why you included a Great Work % boost.
Lastly, I agree that it'd be awesome and super unique to actually have rails factor in somehow using the building, though you have way more knowledge on how feasible anything is in that regard, and as you said, the coding could become quite convoluted or even downright impossible, so I'm just here for ideas.
GRH : +5

/ +2

/ +2
- 50% of the
from tiles/WW/NW is converted into
. -- No gimmicks, just straight to the point by simply amplifying the standard Hotel's function. Your capital / core cities will generally still be the greatest beneficiaries of this aspect, due to usually owning the best terrain alongside GPTI.
- +2
/
for every tile separating this city and the next closest owned city. -- Minimum is 3 tiles between (though, some people do adjust this setting higher for more spacing), so that starts it at +6
(the cost of the standard Hotel, so in effect, this feature grants each city with a maintenance free UB at the very least). Building a GRH in each city is a given, so although the stacking yields are strong, it doesn't really accompany any different unique gameplay because your building them anyways (the Stalker0 argument). I believe my mechanic would bring a bit more flavour and variance, instead of simply stacking yields.
City Connections provide +5
/
to Seaports, and if a Train Station is present, +2
on railroad tiles which form
Capital connections. -- Seaports get an up-front boost so they're not excluded from gaining a bonus, meanwhile, a landlocked city at a crossroads with rail tiles connecting 2 other owned cities (3 rails to each city) would receive 18
which further translates into 9
after the 50% conversion synergy.
These numbers could all still be tweaked -- who knows, maybe my proposal is actually too weak, or my rail idea is moot -- but IMO, I think they're closer to being balanced than the yields you've just implemented, plus they require more 'tactics' than just binging culture in the capital, which most civs do regardless; under your new design, a player's biggest city (probably your capital 9/10 times), with say, 40

from tiles/WW/NW, would be granting 10

/

to each owned city + the stacking yields (e.g., if we assume a decently sized wide empire at 10 cities with a GRH, that equates to +20

/

each) + GRH base yields = 6

/ 32

/ 32

per UB (or 60 / 320 / 320 on a 10 city empire) starting at Industrial. I think that's probably a bit heavy compared to contemporary UB like the Skola or Grand Ecole (I can't recall their yields / features off hand, but I don't think they're
that powerful). I know it's still a late UB, and has reliance on

, thus justifying more power, but I think it's probably over done a tad. I could be wrong though, maybe it's all fine and everything balances/scales well, so ultimately the only way to know is by testing, which I unfortunately won't have the means to do in the near future (I still haven't managed to get halfway through an Ainu game for Hinin).
This is all after first glance; please don't take my critique to heart, as I know you've already done the work for your new update, but I still figure I'd share, just in case you're intrigued.