here (Canada) what you outline is a violation.
https://www.canada.ca/en/employment-social-development/progr...
Changes in Powers or Duties
The most common cases of constructive dismissal are where the employee leaves as a result of material changes in powers or duties. Usually, a main area of responsibility is removed or the employee's duties are decreased; for example, a plant superintendent whose duties are confined to those of yard foreman. Such actions are in fact a dismissal in disguise, whether or not they are accompanied by changes in salary or job title. Commonly, this form of constructive dismissal involves a significant loss of prestige and status as a result of a corporate reorganization or change in reporting arrangements.
Of course, if they didn't change the salary then it could turn out interesting; the customer support folks could demand equal pay as the ex-engineers.
The FT's "solution" was to move hundreds (probably even thousands) of people into call centers and subject them to what today would definitely be recognized as mobbing. A family member went through that - she said that, whoever could quit quickly did, and people who had no alternatives stayed on the job largely only thanks to tranquilizers and other psych meds.
The French managing practice of moving someone in a spot where they will get bored out, if not killed out is called "placardisation," or "to put someone in a cupboard."
Demeaning and morally unacceptable, but something that business majors at French grandes écoles are taught is "une normalité," a given, a fact of business life.