1. No embedded crossovers have gone in; these are the only two. There is one already in just South of the OMSF on the Waterloo Spur, ballasted. There will be two full crossovers ("X's") at both Fairway and Conestoga. The one at Conestoga is unique in that it's more compact than typical (No. 5 vs. No. 8).
2. Their purpose is to permit trains reverse their travel direction; ie, to get back to the OMSF early, if required (ie, technical problems, cleanup, whatever). They are spaced at semi-regular intervals, where convenient. As far as how many: that would be a balance of cost (can't have too many - expense) vs. service impact (too few = loss of operational flexibility).
2. Their purpose is to permit trains reverse their travel direction; ie, to get back to the OMSF early, if required (ie, technical problems, cleanup, whatever). They are spaced at semi-regular intervals, where convenient. As far as how many: that would be a balance of cost (can't have too many - expense) vs. service impact (too few = loss of operational flexibility).