Yellowstone, northern states cellular coverage?

We were in Yellowstone last summer. Yellowstone NP installed/upgraded to a new cell tower system to increase reception/coverage. I cannot find the article right now but if you google it you may see it.

For us, a 15 min phone call in the evening each day to my Mom worked fine from Fishing Bridge RV park. We never looked nor cared about coverage while exploring the park with our kids during the day.