Here in the states the fill tubes are not viewable, since the "country" fill (or gravity fill inlet) is molded into the sidewall.
The tank monitors here in the US are a system of electronic contacts that are indeed drilled into and sealed along the tank sidewall. These are standard equipment on every camper I've ever known about.
We need to fill the tank, then go inside the coach to activate the monitor. These are somewhat inaccurate, since we only get "full", "2/3”, "1/3” and empty indicator lights.
The same type of system is also installed in the waste holding tanks, and those are even more notoriously inaccurate due to the solids usually found in those tanks.
Frankly, a clear viewing manometer-style tube would be brilliant! But the U.S. market would never allow for such a functional, accurate, simple and elegant solution to the problem of tank levels. Is appears the U.S. market much prefers form over function.
That jayco journey looks like a fantastic rig! And add the "outback package" you've got what appears to be a very capable and functional rig.
Craig T. Bailey
2015 Jayflight 32BHDS
2007 Chevy 2500HD Crew 4x4 Z71