Back in November 2011 I asked Mike about this. Given his response it seems that he is saying whomever owns Liard has the ability to control that clause. Our contract specifically states that Teck has the right to make the decision whether to put the mine into production so our ability to force this would have to be limited.:

Q: I was thinking about this agreement between Liard and Teck that we
haven't seen. The one that is states the mine has to be in production
within 4 years. I assume that we will be held to the same agreement when
we get Teck's shares of Liard so we would also have to be in production
in that period? Does this present a problem for us in terms of selling
our percentage because someone is then held to a tight schedule? Or,
would they want to get this into production swiftly anyway so it is a
moot point?

A: You are entering a minefield of legal issues here with no easy answer.
Having said that one has to keep in mind that upon completion of a
positive feasibility study Copper Fox would own about 80% of Liard
(Teck's 78% and the additional shares acquired this year by CUU).