If you have a way of doing so please feel free to share. As of right now the Hunter Street tunnel only has a single track that has the responsibility of running both CP and GO in and out of hamilton. Whilst the tunnel is theoretically wide enough to support two tracks, the tunnel isn't tall enough to support double-stack freight trains in such a configuration (hence why its single track currently). If you want to expand the tunnel to offer more service, there are 2 general ways to do so: Make the tunnel taller so that a track on the side of the tunnel could support double stacks, or make the tunnel wider. The former cannot be done whilst also preserving CP's access to Hamilton GO, so you'd have to somehow build some sort of temporary bypass that CP trains could use whilst work is being done on the tunnel. Then you could theoretically move the track to a side of the tunnel, and deepen the tunnel one half at a time (I'm not an engineer, and there's a really high chance this isn't even feasible, but I'm working with extremely optimistic scenarios here). Even then work could probably be done way faster by just... closing the tunnel and not doing half a tunnel at a time.