Arriving at Canada Water from HOP, the lift (well hidden on the side of the platform) only leads up to the ticket hall. Anyone not able to use the crowded escalator has to go up to the ticket hall, then walk to the other escalator to take the central escalator down to the Jubilee Line from what I can see (let me know if I'm wrong and there is one...) There does seem to be an emergency staircase (which is for emergency use only and locked otherwise). Considering the station was only built a few years ago, it's amazing how they couldn't integrate wheelchair access etc. more successfully and have a staircase in addition (as is the case on the other platforms there).

And the only reason why people haven't fallen on the escalators yet during the morning rush hour is probably because it's too packed for them to move more than 2 inches in the first place. A safety precaution of sorts, I suppose...although it does make for very good entertainment to watch some people rush out of the train and run towards that escalator in the morning...