wiggy,
It's 30 years since I operated that route, and I was no expert then. Looking at my world globe, Iqaluit (formerly Frobisher Bay) looks easily the strongest candidate from the point they diverted.
Half-decent weather for the time of year, I guess:
CYFB 011900Z 32006KT 4SM -SN SCT034 BKN055 M21/M24 A2964 RMK SN3SC1SC3 SLP042
CYFB 011800Z 31004KT 5SM -SN SCT035 BKN051 M21/M25 A2962 RMK SN2SC2SC3 CIG RAG SLP037
CYFB 011730Z 32004KT 5SM -SN SCT034 BKN050 BKN100 M21/M25 A2961 RMK SN2SC2SC2AC1 SLP033
CYFB 011700Z 32004KT 8SM -SN SCT042 BKN100 BKN140 M22/M25 A2961 RMK SN1SC3AC2AC1 SLP033
Having originally departed Zurich at 1230Z, I'm assuming it would have landed around 1800Z (1300L)?
There seems to be an ILS on Rwy 34, which is about 2600 metres (8600 ft) long.