Trust you to be punctual, turning up well into a meeting!
This colloquial expression is used here to point out sarcastically that he has arrived with typical punctuality; he can be predictably trusted to be always late for an appointment.
This is where AmE speakers might say "Leave it to you to be punctual, ..." instead, I suppose? How do French speakers commonly express this idea?
Some common phrases may express the same idea:
Comme d'habitude
Comme toujours
Fidèle à toi/vous/lui/elle-même
Fidèle à ma/ta/sa réputation
So in your example:
Comme d'habitude, tu es à l'heure
Comme toujours, tu es à l'heure
Fidèle à toi-même, tu es à l'heure
Fidèle à ta réputation, tu es à l'heure
The first two are more common, the last two are more "sophisticated", and may be used with a sarcastic tone (especially if used to point out a negative habit with some irony).
