It sounds funny but that's how it works in Japan. Realistically though there is no chance of that happening with the network as it currently is. That's not to say we can't plan future subway line with interlined operations in mind; I am just not going to hold my breath with it happening since it would require some real outside the box thinking for us North American folk (and I wouldn't be surpirised if no one at the TTC or even Metrolinx is aware that it is something done in some parts of the world; even if that's just me being cynical about the people in charge of our transit networks). I guess any idea of interlined operation died with the City blocking the inerturban lines from entering Toronto back in the early 1900's due to the city despising Sir William Mackenzie who just happened to own every interurban in Toronto at the time. Its not really that new an idea either in North America when you consider way back in the day the North Shore Railway was interlined with the Chicago L giving people a one seat ride from Downtown Chicago to Downtown Milwaukee.And instead of catenary, electrfy via Third Rail. That way, TTC subway vehicles can finally run on GO tracks. It also mean Ford's dream for a subway to Pickering can finally be realized.