This action would be started from November 1, 2015.After November 1, mobile web pages will not be considered as mobile-friendly, if there would be an app install interstitial covering a major proportion of content. As an alternative, the browsers must provide different ways to promote the app which will be user-friendly.So, Google Chrome-supported App Install Banners and native Apple-supported Smart Banners are mobile-friendly in Google’s perspective. Only those banners which cover significant portion of content are not mobile-friendly.
Therefore, it is important to use mobile usability test and check whether your web pages pass the mobile-friendly test or not. This will help you identify, if you have any problems with app interstitials and ranking.
Thus, only those app ads which block or cover a major part of content can lead to a decrease in mobile ranking. Other ads that are not for installing apps are fine.