Here's a quick list of how to meet other x-c skiers. While it's specifically for Ottawa, it may give you some ideas for other cities.
1. Ottawa Outdoor Club
They have events at Mooney's Bay and also meet at Sandy Hill CC to go x-c skiing in Gatineau
2. Ottawa Ramblers
They meet downtown Ottawa to do some x-c skiing in Gatineau. The outings indicate the experience level recommended.
3. RA Ski Club
They meet at RA Centre to do x-c skiing in the Gatineaus and sometimes the Greenbelt.
4. Ottawa Meet-Up Group
I've seen some specifically for x-c skiing in the past but there are also outdoor activity groups.
5. Reddit thread
I've seen threads of other Ottawa locals looking for skiing partners. The last one was for women aged mid-20's to mid-30s.
6. Ottawa Section of the Alpine Club of Canada
They meet at Parkdale and Emmerson to do some night x-c skiing in Gatineau.
7. Winter Orienteering
Some of this is done on x-c skis and they have some events in the city including the Winter Solstice Charity Challenge at Lincoln Fields and some orienteering on the Canal.
Do you have any other ideas? Are there apps available now?
Wild. Here. Urban Cross-Country Skiing Series 2017
PART ONE - Four Places to Cross-Country Ski in the City
PART TWO - Cross-Country Ski Basics and Local Rental Locations
PART THREE - How to Find Other Cross-Country Skiers