Product documentation identifying what is proprietary, design and version-control records showing the engineer's contributions, internal training materials with the time they take to complete, and the subsidiary's staffing description. These are more persuasive than the engineer's résumé.
Let the company's own paper trail prove the knowledge
Hypothetical example: the company realises that most of its calibration logic exists as code and in a wiki that only staff can read. That is useful evidence, not a problem. The petition can include screenshots or excerpts of design documents showing the engineer as author, a commit history summarised in a table, and an internal architecture overview marked as confidential.
A training plan for new engineers, with the modules and their estimated duration, demonstrates how long the knowledge takes to acquire. The Oregon subsidiary should provide an organizational chart listing its technicians and their functions, so that the gap the engineer fills is visible. Corporate evidence sits alongside: the share register proving the parent-subsidiary relationship, recent customer contracts and payroll for both entities, and the engineer's Canadian payroll history covering at least one continuous year of full-time employment in the last three.
Her degree and résumé go in the file, but as background; a petition that leads with credentials and treats the product as an afterthought has its priorities reversed.