FORUM

Yes. Good question! One way is as a formal master-apprentice relationship. An apprentice's spells don't interfere with her master's spells, and vice versa. But the apprentice gives up a lot of power to the master. The master can modify, weaken, or augment an apprentice's spells; he can punish her in several ways (mood penalties, histories, limited spell selection); and he is automatically an inspiration for her. Of course, the apprentice gains spells through the relationship, so it may all be worth it to her.

Another way that interference can be avoided is through magic organizations. There are seven different types of organization in the game (noble house, secret society, trading company, etc.), and magic orders, covens, and cabals are one of them. Usually, wizards of the same cabal interfere with each other, but if they take the right precautions or use the right spells, cooperative casting is possible. Rank is especially important; a higher ranking cabal member is more likely to be able to ignore a lower-ranking member's spells. Covens and cabals are especially conducive to high spells, which are the longer more ceremonial spells, rather than the quick combat spells..

There is also at least one building that you or your organization can construct that allows you to use another wizard or other wizards to help you cast your spells. It's not a kind or even voluntary process, however.

There are probably a few other cases as well. Interference is the default, but there are ways that wizards have found to work around it. Nothing that removes the threat of it from society completely, but there are ways to mitigate it, especially if one magic cabal seizes power in an area and exterminates the competition.