Hello Aspirant ,

Non-Engineers have equal chance as an Engineers , sometime Non-engineers have higher chances than an engineers  as these IIMs prefer academic diversity among students , but you need very high rank and percentile(99.5+) to get into IIM A,B,C in CAT exam .If you do get very high percentile , no one can stop you from admission so prepare for it without any fear , non engineers will be treated just like an engineer.

The selection is also based on many other factors like your past academic record , work experience etc.

Hope this helps.