I write evidence summaries for a renowned institute which makes me an author for every summaries. When I contacted team, they informed that it is a grey literature. I wanted to know if I can count it as a publication and cite in CV as such?
Evidence summaries are not research papers. Preparing them will teach you to be critical and how to summarise and write clearly, but they lack other crucial aspects of research and research papers, so they are not research publications. (Research authors generate a research question, express it as a thesis statement, decide what variables are involved, collect and analyse the data and submit the report for refereeing).
In North America, generally, it does not. However, you can still add these pubs to your cv to show that you are active in the professional community which is a good contribution by itself. However, it will never help one getting a faculty position or tenure.