I don't know how widespread that is but, anecdotally, the idea that you would lean on a staffing agency to quickly pull together a team is not bizarre.
One of the things I've learned from the research and speaking with public servants, both in Canada and internationally, specifically about this question of how governments can responsibly work with private IT vendors is that once you have that core expertise in-house, you're in a great position to be that smart shopper, to compile those teams yourself and know which firms have expertise, who does good work, how to check their work and hold them to account. You can then directly build that search capacity—which is a term that often gets used by public servants—acknowledging that, especially when something needs to be done really quickly or there's an emergency, as was the case here, of course you're going to work with private vendors.
I don't tend to hear anybody telling me that working with an intermediary like a staffing agency is what they would view as best practice. That's all I will say about that.