They'll happen but they won't bring down the government or anything close. Given that the vast majority of union members are public employees, and given that the people most badly affected by strike action will be ordinary people, all that will happen is that they lose sympathy. It's something of a dog-whistle reaction on the part of the unions, unfortunately. Channeling Arthur Scargill in some cases, with lofty aims of 'bringing down capitalism' LOL. Holding out for higher pay, early retirement and better pension terms is all well and good, but if it means that half your members end up in a dole queue, have you really done them any favours?
The trouble with one day strike action is it doesnt really have an impact on service delivery. For strike action to be effective it needs to be all out for a period of time that will cause absolute chaos. Sadly most public sector workers (Am talking AA/AO/EO level- those that actual are the backbone of the delivery of most of the services) will not be able to afford to strike long term as they simply cannot afford to.
My grade for example AO/Band B the max is 18K - we work very hard for that money with very few thanks. As someone posted a couple of days ago, years ago, the Civil Service was a "job for life" with many perks, flexi, and a good pension, which you could theorectically take from age 50 if you had enough years in (albeit at a reduced rate)
Sadly most of the "perks" have slowly been stripped away over the last 10 or so years, and you are left with a bunch of disheartened workers with very little morale trying to deliver ever increasing demands from management under ever increasing pressure for very little thanks. We are now entering year 4 of a pay freeze, while the cost of living has rocketed around us
And for most people who work there leaving is not an option- theres nothing else to go to. I'm not in the Union at the moment- when I was a member I actually disagreed with the strike action as I was happy with my conditions of service and pay etc (I am of the opinion that if a strike is called all union memebers go out)- I was asked to leave the union if I wasnt supporting the strike action, but as things become more unsettled within the public sector I think I will have no choice but to join again