Having previously responded to similar questions in previous appearances before House of Commons and Senate committees regarding other punishment bills that such answers could not be divulged as they were matters of "Cabinet confidence" (read here), Head took it one step further stating that "[g]oing back and trying to find specific data... that gives us enough information to say that this bill is going to equal X number coming into [the] correctional system, there just isn't enough data for us to do that" (read article by Stephanie Levitz).
Given that this is the third time this bill has been tabled (see C-26 - 39th Parliament, 2nd Session; C-15 - 40th Parliament, 2nd Session), it is hard to believe that government officials do not have, at the very least, a rough idea of the impact of this legislation on CSC institutions and related costs. After all, it has been almost three years since this legislation was first introduced into Parliament - plenty of time for CSC to gather the necessary data.
So again, Senators are in the position of voting for a Conservative punishment bill in the dark, not knowing the potential influx of prisoners that may result from the law should it be passed. However, they do know that there are many substantive problems with this bill, not the least of which is the fact that "[s]evere MMS [mandatory minimum sentences] seem to be least effective in relation to drug offences" (read 2002 Justice Canada report, section 9.5).
One would think that given the substantive and procedural issues with Bill S-10, that Senators would stop this legislation dead in its tracks before it is sent to the House of Commons for their rounds of votes. However, now that the Conservatives have the majority in this chamber, it will likely be up to the majority opposition MP's to have the political courage to scrap this piece of trash masquerading as legislation that will enhance 'public safety'.