Under the current system, if a political party can get more than 50% of the vote in any riding in the Greater Toronto Area (GTA) it does not produce any more Members of Parliament (MPPs) for that party. That is because each riding only elects one MPP. Therefore, a political party in that situation would shift its attention to other ridings in order to gather support. That is the essence of the first-past-the-post system.
However, that is not true with the additional 22 'list' MPPs that the proposed system will create. There will be much more emphasis on vote rich GTA because now every vote, even in a riding where you have more than 50% of the vote, brings you closer to an additional MPP. And that is one of the cons of the mixed member proportional system (MMP) - and it is a big negative for democracy.
Moving towards a MMP system will not be good for rural Ontario.