First, assuming the CMAs pre-empt TAR, and that 12 legs means 12 episodes, then the finale would be May 13th. The CMAs will be an the halfway mark (six legs) so I tend to think May 13th is more likely. Survivor has been on the Sunday before Memorial Day weekend, and it'll be close to or the last day of sweeps, and that finale has done well in the past.
Second, Canada also goes onto DST in lockstep with the U.S.
Third, next Sunday is selection Sunday for the NCAA Tournament. CBS is airing this show which is done live. Some tournaments may not be totally completed It looks as if CBS may be airing the finals of the Big 10 tournament before the selection show, also live.
In other words, there's an off-chance of things running over because there is no local programming, apparently, for the CBS east coast feed -- there will be at least two conferences airing tournament championship games on CBS that afternoon.