Original Post — Direct link
over 3 years ago - /u/MoltonMontro - Direct link
  1. If the mod creator has made it so that they can spawn on the map you're playing on, they'll spawn.

  2. If you're playing on a custom map that has manually added spawns for that modded content, they'll spawn.

  3. If you downloaded a mod that specifically adds spawn tables for that modded content, they'll spawn (assuming the spawn tables are relevant to whatever map you're playing on).

If it can spawn, the mod author will usually specify so in the mod description.