It depends on the situation.
Mr and Mrs Smith notice their Son has an increased interest in faith, they may be happy and ask Fr Mike...
We're very happy Tom is going to Mass and getting involved in his parish, we hope he's also going to confession aswell, is he?
There would be nothing wrong with Fr Mike revealing that Tom has been attending the weekly confession services.
He would not be betraying Tom, just like Geremia's example of St Catherine of Siena it only adds to the positive image of the person.
One day Fr Mike heard Tom's confession and the worst thing revealed was that he failed to wash the dishes at home.
A few weeks later Fr Tom gets an informal knock on the door from the police, they're asking if Tom revealed a violent murder.
So Fr Mike tells them...
I can't reveal what Tom said, but he definitely was with me at that time in a confession service.
Therefore freeing Tom from the suspicion of the police.
In both of these examples, Fr Mike has not betrayed the penitent in any way, either contributed to their positive image or saved them from unfair punishment. Not in any way in detriment to Tom.
So yes, a preist can reveal that someone has attended a confession service.