Several references:
CAO 40.1.7 Sections 4.1A, 4.1B & Appendix 1 Section 2.4
CAO 40.3.7 Sections 2.1& 4.2.2
Civil Aviation Safety Authority - Pilot Log Books
"Mutual Instructor Flying Involves two pilots who are qualified on type, flying together for mutual practice on a flying instructor course. One designated pilot may log time in command and the other student instructor may log time as co-pilot. This flight time may be included in the Grand Total Hours."