Depends what it is done. It could be implemented in a more structured way than escrow of, say, an entire account would be. For example the ability to open spe

Depends what it is done. It could be implemented in a more structured way than escrow of, say, an entire account would be. For example the ability to open specific mails, specific conversations or with specific other parties under particular conditions, without revealing metadata of the rest. Or conditions like "if the person X communicated several times in a month with person of interest Y during the time crime Z occurred, open it up, but don't reveal the existence of anything outside that". You can think of that as escrow of each message separately and just enough to match which messages you're looking for, while keeping the as much as possible about the others private. But actually doing it takes sophisticated cryptography still at the leading edge of research.