Picloram, product name Tordon
Yes, picloram has been known to kill plants when contaminating compost. As of 6 March 2020, a PMRA label search indicates there are still 8 picloram products registered in Canada: 7 commercial and 1 technical active. None are restricted. Products are sold under a few names: Tordon, Ram, Grazon and Aspect.
Various products are used for application to rangeland and permanent grass pastures for perennial weeds and/or rights-of-way only to control unwanted brush and broadleaf weeds.
March 2020: 'One of the chemicals that Coastal Gas Link is asking permission to spray on their new pipeline route through endangered caribou habitat and pristine British Columbian wilderness, is Tordon 22K, a picloram-based herbicide. This stuff leaches into groundwater and is known to persist. (Stop the Spray BC)
I believe it is still used by Sask Power under power lines ( don't quote me on that). Obviously still used in agriculture. How much is used in SK or Canada is anyone's guess.
Picloram (Panna Pesticide Data Base) is considered a bad actor chemical. a groundwater contaminant, and a suggested endocrine disruption chemical.