If the MBBS certificate is written in English then it meets the requirements for proof of English knowledge. If it does not you should get a letter from the school that indicates the language of instruction was English:
- A degree, diploma, certificate or official transcripts from a secondary or post-secondary education program showing you studied in English or French, in Canada or abroad.
- If the original document is in a different language, include:
- a letter from the school showing that the language of instruction was in English or French along with
- an official translation of the original document and
- the address and contact information (phone number) of the education institution
(from
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides/guide-0002-application-canadian-citizenship-under-subsection-5-1-adults-18-years-older.html#language)
If your certificate is not in English, and if that letter and possibly translations are difficult to get then it maybe faster (and cheaper) to take an IELTS or CELPIP test (someone else on the forum recommended to take the CELPIP-General LS, as that only tests listening and speaking... so it's a bit cheaper).
IRCC does accept an expired language test if it was used for immigration purposes, but I take it you do not have a scan or photocopy of the test result. I don't know if they would accept a letter explaining you submitted the IELTS result with your PR application (as they should have that on file). Hopefully someone else on the forum has been in that situation and can chime in.
