To answer and clarify:
The alternate list is formed throughout the interview process. Pacific will often inform people that they are interviewing for a slot or interviewing for an alternate position. A lot of the February interviews were for alternate positions. I don't think Pacific gets back to you about whether, based on the interview, you are on the list, but I'm sure you can call and find out if you are on the alt list at this point.
And what armor said is correct except the date he forgot to mention was May 1st. On May 1st AADSAS or the ADEA or whatever organized dnetistry body does it, will find out from every school who has put down HOLD deposits at those schools. If a students has more than 1 HOLD deposit on May 1st, each school that student has a deposit at will be contacted and told that student John Smith has held positions at School X, School Y, and School Z. At that point, the school will contact the student and ask for a final decision within 2 weeks. If the student does not contact two schools to release their HOLD and commit to one school, the schools have the option on May 15th or so to drop that student from their roster of incoming students and select another student off the wait list.
Crossing my fingers until May15th!!! 
