Case I port holding pattern altitude

[Hippo]

According to the CV NATOPS, 6.2.1,

Quote

Flights shall be established at their assigned port holding pattern altitude 10 nm prior to entering the pattern.

How does this work IRL, i.e., how and when is this altitude assigned?  And what to do in the (single player) game?  I normally just use 4.000 feet and wait for "charlie", but should this altitude have been passed to me by the tower on entering the CCA?  Another one for the wish list?

A recent mission I played had five other, single aircraft, AI flights arrive at around the same time as I did.  One AI went straight into the landing pattern (i.e. 800ft), the other aircraft went into the port holding pattern at 4k, 5k, 6k and 3k.  I was behind them.  How was I supposed to know which levels they were going to use?  How was I supposed to know which level I was supposed to use?

Edited 4 hours ago by Hippo