Unless you've been able to apprehend the accused immediately, do all the tests and ensure what his alcohol and drug levels were, which is rarely the case in sexual assault, the Crown simply won't have the information as to how intoxicated the accused was at the time of the event. It's just not going to be there.
Given this legislation, meeting that threshold of substantial likelihood of conviction is going to be very difficult in cases where the accused was very intoxicated, even where the standard of extreme intoxication might not necessarily be met.