I believe almost all lines can support 25 Mbps + TV, so there wouldn't any need for sharing. MTS will bond 2 lines to provide the necessary speed if needed, but there is significant extra cost - 2 copper lines to the fibre-optic node and 2 line cards in the node.
The attainable line speed depends mainly on the distance from your home to the node (the length of the copper wire) and also the thickness and condition of the line.
For example, I live close enough to the node to get about 75 Mbps on a single line, so if I ordered 50 Mbps internet, there would be enough capacity for me to have all TV streams active and still maintain a constant 50 Mbps internet speed. If I lived slightly further away and the attainable line speed was below 70 Mbps, I would see a maximum speed slightly below 50 Mbps if I had all 3HD streams active. MTS wouldn't authorize a bonded line in that situation. However, if I lived considerably further away and I ordered 50 Mbps internet and TV, MTS would probably authorize a bonded line, assuming the extra line and space in the cabinet was available.
Last edited by Dr.Dave; 2016-03-09 at 08:16 PM.