In many cases, 'estar de par de' is simply translated as 'know' of 'to be aware of'.
For example: 'He knows everything about the situation' or 'He is fully aware of the situation.'
The nearest set phrase we have is the borrowed French expression, to be 'au fait' with something.
For example : 'Are you au fait with the situation?'
Another phrase, used a lot in business contexts where the situation may be constantly changing, is 'up to speed'.
For example: 'Are you up to speed with what's happening on the ABC project?'.