"But it looks like GWT goes East from Lees Ferry, bypassing the Page area"
I assume you meant West and not East. In the GPS file I have been creating with waypoints taken from either the "official" map or Benchmark maps I show it following 89A up into the mountains and then north on forest road 278 up to Winter Road. Last year we saw a big GWT sign at the intersection of Winter rd and House Rock Creek rd.
I show it crossing 89 about 6 miles east of Johnson Canyon road on Seamon Canyon road. But none of my GPS maps show a road going thru as it continues north.
I do not believe it goes up Smokey Mountain Rd from Big Water to Escalante as I think Jerry shows on his map.