You can suppose that owners of the same type of holding will oppose you, unless you have an agreement with them saying otherwise.
Law holders should be, I think, neutral by default. When you have a treaty with them, they can support you. When you are their enemy, they will likely oppose you. If they prefer another regent with holding of same type, they can oppose you as well. For example if you are trying to create a temple in Medoere theocracy, you can count that other temples as well as local law will go against you.
However, best way is to ask DM.