Update 30 March 2020 Heller is now before the SC, and the British Colombia Supreme Court distinguished it in Williams v Amazon  BCSC 1807, holding as McCarthy Tétrault LLP report that the arbitration clause provided for a refund of costs in many cases. Further, the arbitration could be conducted through flexible options, and as such, this was not a substantially unfair bargain so as to meet the test for unconscionability.
Thank you Christopher Burkett for alerting me to Heller v. Uber Technologies Inc., 2019 ONCA 1. The case is reminiscent of California’s Senate Bill 1241 (review here) and of an article that I co-authored with Jutta Gangsted [‘Protected parties in European and American conflict of laws: a comparative analysis of individual employment contracts]. The starting point of the California, the EU rules, and the Canadian judgment is the same: employees cannot be considered to really consent to either choice of law or choice of court /dispute resolution hence any clause doing same will be subject to mandatory limitations.
Here, an arbitration clause requiring arbitration in the Netherlands of disputes between drivers and Uber was held to be invalid and unenforceable, because it deprives an employee of the benefit of making a complaint to the Ministry of Labour under relevant Ontarian law.
Of note is that the judgment applies assuming the contract is one of employment – which remains to be determined under Ontarian law. Of note is also that the Court of appeal rejected Uber’s position that the validity is an issue for the arbitrator to determine because it is an issue going to the jurisdiction of the arbitrator. Uber invoked the “competence-competence” /kompetenz kompetenz principle (recently illustrated e.g. by the Brisilian Supreme Court in Petrobas) in support of its position.
(Handbook of) European Private international law, 2nd ed. 2016. Chapter 2, Heading 220.127.116.11, Chapter 3, Heading 3.2.5.