MTS has long sold all consumer internet as "speeds up to" which is what is being described here. There are similar issues is more urban areas too with poor line quality or other issues limiting the actual speed of the service.
In terms of the claims that Manitoba is behind the rest of the world when in comes to internet service in rural areas I would like to point out that this issue is very common across the fourth main companies in Canada. The United States, which is culturally similar, also has significant issues providing service to rural residents. The challenge is, especially in Canada and parts of the US, rural areas tend to be further from larger urban centers and residents tend to live much further apart from each other. Both these items make providing urban levels of service in rural communities very cost prohibitive and the $70 a month doesn't go very far when you are the only customer for several miles of cable.
Think of a wireless router. If you are standing right beside it, you get pretty good signal and speed. If you're 100 feet away from it, your signal and speed is not as good. In both cases, it costs the same amount of money to buy the router and connect it to the network, even though the speed may vary. This is similar to internet service in urban vs rural locations.
To my knowledge MTS owned stores aren't selling boosters but franchises operating MTS stores might. Wireless towers can have directional service which can be changed. The other piece is that a tree growing taller could block out signal. If you are in an area where a booster is needed to get service keep in mind it is already on the edge or even outside of the coverage area. MTS has offered to look at the signal pattern of other customers and would likely for you as well. There is only so far they can take things though with troubleshooting privately owned boosters.