Whether a CA is eligible for CAT?

Nopes. You need a UG degree to be eligible to apply for CAT

NO GRADUATION ARE NECESSARY

Qualified CAs, ICWAs, CSs are eligible for appearing in CAT. Most IIMs also give additional credit for the work experience during the training and for non engineering professional degrees. Please see the admission policies on the individual websites for details. These policies vary from IIM to IIM.

CAs are also eligible for Government jobs and exams, like Civil Services, which require graduation as an entry point.

This requirement of an additional graduation is an old myth being perpetuated by those who are not updated.

Serious students should not waste time and energy in acquiring additional qualifications initially. BCom, at best, is a back up degree if you fail to make it in CA. It adds an additional value - the fun and learning from being part of a college. But where is the time during (non dummy) articles?

CAs are given more priority then any other course in IIMs...so just chill, CA degree is equivalent to post graduate degree, and u can go for doctoral course also in IIM, forget the eligibility infact CA have edge over others for CAT....I have read this in ICAI brochure, CA rocks