You have to keep in mind that when electricity was nationalised in Québec, it did not start in the 1960. The government of Adélard Godbout enacted the Act acreating Hydro-Québec in the 40s, which included the acquisition of some gas companies and other in particular in the greater Montréal area.

When Adélard Godbout made the announcementthat he would nationalise electricity, he made sure to wait for the markets to close: clearly, there was a will to keep this under control but my main goal with this small intro is to show that the nationalisation under Jean Lesage was not the beginning but the follow-up of a process who started 20 years before.

As such, in the 60s, René Lévesque was ministre des Ressources naturelles (minister of natural resources), and convinced Jean Lesage that all of electricity should be nationalised and developed by Québec for many reasons but one of them to remedy to the fact that French-speaking engineers and managers were unable to get hired by companies dominated English-speakers but also (maybe most importantly) to remedy the chaotic nature of the price structure and the organisation of power companies in Québec. It was a way to ensure that the majority of Québec would benefit of the rapidly increasing importance of electricity and put some order in the whole ordeal.

Now, in order to nationalise, they were planning to buy the shares of the various companies. In order to do so, they went to New York and Paris and see if they were able to secure a loan to buy all the remaining private companies. Once they got the "ok" from the banks, they had the logistics to buy back the companies to effectively nationalise.

Why am I explaining this process? Because the buy back was quite a soft one. It was not forced expropriation like we saw in communist countries; companies were going to be bought back as per market price. Of course, there was a lot of PR from power companies who, for the first time, had to to PR in French and were accusing that Jean Lesage was a socialist government and Québec nationalism was a path to communism and the like.

Following the 1962 election, with a strong approval from population to go ahead with the nationalisation, they waited for the markets to close to make offers to the various companies. They complained that it was not enough but most economists agree that the price was in the end fair. Utility companies did not take a big hit nor did the Canadian dollar; Québec emitted bonds to pay its obligations to the shareholders of the companies they bought out. The whole thing was done in collaboration with American authorities to minimise the impact on the stock markets and on the value of the CAD. So although the reaction was an ideological opposition from the international business community, it was done properly and any accusations of socialism or trying to stiffle private entreprise were more of a PR-related thing in Québec or Canada than something that worried investor in the long term who, if anything, took the opportunity to buy the bonds emitted by Hydro-Québec and in the ended profited off it.

Sources:

Paul Sauriol, La nationalisation de l'électricité;

Some info was double-checked using Hydro-Québec's website;

Jean Lesage et la Révolution tranquille