Incident at Saskatoon, Saskatchewan (ATS operating irregularity)

1996-11-29: West Wind 200 was enroute Saskatoon from Key Lake. West Wind 7, a HS748, was conducting IFR training at Saskatoon. The crew of WEW200 had been cleared to maintain 3200 feet for the ILS approach at 2 miles from the beacon. WEW 7 had been cleared to maintain 4200 feet and not to descend until further advised. While both aircraft were approaching each other, the crew of WEW 7 descended, ATC recognized the altitude deviation and re-cleared the crew of WEW 7 back to the original altitude. The aircraft came within 600 feet vertical and 3/10 of a mile horizontally of each other. TSB are not investigating, however, ATC are planning a fact finding board.