The plan I described does not include calling from the US. If you want a border-transparent cellular plan, 20 GB is as big as it gets for Telus. They can't offer you something which does not exist.
From what I can see, none of Telus' competitors offer a Canada-US plan anymore. The only 50 GB plan I could see from any of the competitors Included Canada and US calling from Canada. You have to buy roaming options for travel.
Bells offer the 50GO plan at 115@month, +20$ you make the plan CAN/US, it exist at rogers too...
It's well hidden on their websites, then.