At one point, it was possibly to get all the ExpressVu channels with a Dish 500 in the USA, and the exchange rate was also favorable for the US, so a number of people subscribed through "brokers" who used their Canadian address to receive the bills, and then charged a fee.
THEN, ExpressVu had trouble with their satellites, and leased a lame satellite that didn't reach the SW US and moved some of their channels to that satellite. At the same time, the exchange rate got worse for the US and also ExpressVu raised their prices and their minimum package price. So, a lot of "Southern" ExpressVu subcribers left at that point.
Ironically, during the same period, StarChoice started out not being feasible in the southern US (which led US residents to pick ExpressVu instead). But they upgraded their satellites and are now easily picked up throughout the US with normal Ku band 30-inch dishes (from what I have read).
Both ExpressVU and StarChoice (like all subscription services) require use of their own brand of receivers (easily obtained on ebay or from online retailers who will ship to the US). Both services require Canadian billing addresses, otherwise they would be in violation of Canadian law.
The exchange rate is no longer favorable for US residents, so these days, people subscribe mainly in order to get Canadian programming not available in the US.