Is Gmail on Android susceptible to MITM attacks?
Indeed, overriding certificates it's one of the most popular ways to compromise https. So, if your employer can succeed to create a certificate that fools the app, it can easily perform a MiTM attack.

Some links to check about mitm attacks on gmail app:


[1]: http://www.networking4all.com/en/ssl+certificates/ssl+news/android+apps+vulnerable+to+man-in-the-middle+attacks/
[2]: http://bgr.com/2011/08/30/iranian-government-said-to-be-using-mitm-hack-to-spy-on-gmail-other-google-services/