Various online discussion suggest that this 'customer satisfaction" campaign - identified as N150036 or 15036 - is internal to General Motors, so it is not a recall reported to Transport Canada or NHTSA. GM seems to be pre-empting a potential problem, rather than reacting to a history of failures; that's good and responsible business operation.
Z82 is simply the towing package, consisting of the hitch and wiring (and locking diff for those trim levels that don't already include it); any of these trucks with a factory hitch has regular production option (RPO) Z82. It's hard for me to imagine buying one of these trucks without the towing package, and it's standard equipment on all but the lowest trim levels anyway, so it should cover most Silverado and Sierra trucks in the affected period.
In case anyone is curious: 2014 Chevrolet Silverado standard features and options