Blizzard has confirmed that the absence of the Catch the Wild Wolpertinger and Pink Elekks on Parade quests on European realms is not a bug. These "get drunk and see creatures" quests were removed to comply with "regional game rating requirements". We can surmise from this that at least one of the European countries is unwilling to allow virtual inebriation in a game partially targeted to teenagers.
We usually think that the U.S. is more prudish about these kinds of non-violent topics than Europe, but obviously that is not the case here. Personally, I think these quests are pretty innocuous and the near blindness you get when you get hammered in-game isn't exactly encouraging young drunkenness. But I do see how some would disagree with me.
We are researching this, but in the meantime, do you know which region(s) are causing the removal of these Brewfest quests from Europe?
Update: Wednesday morning before the restart, many people were able to do these quests. But after the restart, the quests disappeared again as intended. It looks as though those who did the quests were able to keep their tokens.