No, there have been all kinds cases of enforcement action in EU where the user was informed but the employer could not justify the violation of privacy; in general EU law and especially in privacy law it's quite frequent that some explicit "consent" clause in employment contracts (essentially, if it's a standard clause in all agreements and "take it or leave it") is treated as not representing true consent and void.

The largest example probably is the 2020 GDPR fine of 35 million euro for clothing retailer H&M for violating the privacy of their employees, despite the employees being informed of that.

What you're talking about has absolutely nothing to do with tracking usage of workplace computers and networks - H&M kept "excessive" (sic) records of personal data of people who were not their employees at all (family members of their employees) - and the problem wasn't that they had some data because in EU you're required to keep track of families of your employees due to tax reasons, but that they had too much of it.

In most EU countries, tracking company-owned hardware is explicitly okay, and where it's not mentioned in law there are judicates that make it OK.

As I said, even the government and its wholly/partially owned enterprises are doing it, and working as a contractor for the government here requires you to track usage of your employees' workplace computers too, so I can't see how it could be in any way illegal. Same thing with working for banks and insurance, and I bet there are more cases.

In The Netherlands, employees enjoy a reasonable level (much stronger than this scenario) of privacy even on company equipment [1]. That is: the company cannot randomly access an employee's mailbox. Of course, in case of employer-employee dispute, things become hairy - but even then, the company is not allowed to go on a fishing expedition. Though they can go on a confirmation run, looking for specific evidence, e.g. mail from Glassdoor.

Don't know about other EU countries, but at least NL deviates significantly from the sketched scenario.

[1] https://blog.iusmentis.com/2017/11/22/wanneer-mogen-mailbox-...