Carcassone city score when tie
When multiple players score a feature, each player gets the full amount.
There is only one way to score a feature, and if the rule says that each player scores that feature, each player will get the full amount of points. Every feature that can be shared (city, road, farm) has the potential to have a number of points such that an even split would be impossible to begin with.
For example, finished cities with a cathedral triple its score, so you can end up with an odd score for that city, making it impossible to evenly split between two players.