This is a good example of how information working in one category flows over into another category. We currently have reasonable capacity to pre-screen individuals who are coming to Canada in some acceptable category of immigration. However, we don't grant visas to people to come to Canada to seek refugee status. You can possibly be a resettled refugee and you can be extensively pre-screened in that way. Those people who are government-assisted refugees are probably subject to the highest screening of any group at all. Mass arrivals on boats—to come back to where your question started—are the groups of people about which we're going to know absolutely nothing before we start. One way we could think about gathering information about those individuals would be to create a visa category that allowed people to come to Canada to seek refugee status. That would be something.... I've only ever heard of one other country in the world—I think there are limited opportunities in the Swiss system for this capacity. That would allow pre-screening of people who were going to seek asylum in Canada.
Aside from that, it's not a question of the kind of information we seek in advance but rather that we don't provide any way for people to get into an immigration category. Those people we are most concerned about are the ones who existing pre-screening is least likely ever to get to.