I got the confirmation from the Product team that -
The capability of getting VM eviction rate through REST API is currently not available, but it is on the roadmap.
The official documentation will be updated when that is released.
You can also check Azure updates page to get the latest updates on Azure products and features.
Hope that helps. Let me know if you have further questions.
----------
Please accept an answer if correct. Original posters help the community find answers faster by identifying the correct answer.