You can use elements in the linked model as references for dimensions and alignment.
For example, you can create a dimension between a wall in the host project and a wall in the linked model. See Permanent dimensions and Aligning Elements.
You can also create constraints between elements in the host model and elements in a linked model. For example, you can constrain a linked building to a property line in the host model or a linked floor to a level in the host model. Linked models move as an entire entity when the element to which they are constrained moves. Constraints on a linked model (or an element in a linked model) only move the linked model, they do not move elements in the host model. Constraints to links using shared positions are not permitted.
Revit attempts to retain and rehost dimensions and constraints when you reload (or unload and reload) a link.