Variable! Tends to be down to the event organiser. For stuff like the big european team events they tend to publish a few weeks in advance, but this is partly due to the matchup system they use per game (i.e. one side puts a list forward, the opponent puts two to chose from for the first side to pick from etc), and also to give people a heads-up if they need to review specific lists they're not necessarily familiar with. Also gets a bit of pre-event banter going as well
Last year i think we all got given a pack with the lists in, which was nice too
Normally you'd at least look to put up a breakdown of armies by team, as that in itself can make for interesting speculation!
