Not sure why that matters. Whatever you're using to generate your references, you should be able to define a range for each table? Whether they're to start with a different letter, or number, or one be odd/one even for the numeric part or whatever meets the requirements for that field? That would be best for performance.

Thinking about this further, the restrictions of indexed views make this difficult. If you can't use a check constraint and control your inputs, then a separate table with the reference as the PK, referencing it as an FK in the other two tables would be more appropriate.