Private to Public sector: Salary

How is that even legal?

Yes, that is how the Irish public sector works at this time

Agree that it's absolutely not how to hire the best people. But that's not the goal.

There has never been a law preventing employers from discriminating between the people they employ and the people they don't. If there were, every single vacancy would have to be advertised and be the subject of a public competition; none could be filled by internal promotion or transfer. It would be a nonsense.

Discrimination is only unlawful if it's on one of the prohibited grounds - age, sex, race, religion, family status, etc.

If you want to at the top end of a scale you'd be better aiming for jobs that will get you the bottom of the next scale.

As fits says, there is a process for appointing people at above the entry grade on the scale if they have particular experience or are otherwise especially desirable candidates. It happens reasonably often, depending mainly on how tight the labour market is. But it requires the employing authority to make a case, and it's not something they can or ever do offer in the job ad, because at that point no case has been made.

This tends to come up a lot from people with lots of private sector experience.

Unfortunately the answer will be, you are expected to start to the minimum scale or the hiring department will make a case for you. You won't know until you actually interview and an offer is made.

While I'd agree this can prevent them hiring certain candidates, it does mean they tend to retain people a lot.

Yes, but this is one of those "true but trivial" things. There's nothing wrong with discrimination unless it's done on grounds that we consider objectionable. If you think about it, the entire process of filling a job vacancy is inherently discriminatory.

There's two parts to this,

...equally qualified and suitable candidates are paid different rates of pay...

Why not?

You have to ask why would someone earning more in the private sector want to leave it and join the public sector. If private is better why are they looking at the public jobs in the first place. Especially something at much lower salary. There is something driving them out of the private sector. There is some "value added" about the Public Sector thats making them look.