In this paper, we quantify integrity for a GNSS-PPP system when augmented with mega-constellation satellites (GNSS-MC). The geometric diversity provided by signals from fast-moving LEO satellites is exploited for rapid estimation of floating valued cycle ambiguities. Further, the improved redundancy provided by mega-constellation satellite signals in addition to GNSS enable e cient fault detection using carrier phase Advanced Receiver Autonomous Integrity Monitoring (ARAIM). The proposed framework assumes that mega-constellation (MC) satellite orbit and clock determination is based on their spaceborne GNSS receivers. We quantify the impact on integrity of GNSS faults, which not only a ect the potential users on earth, but also the spaceborne MC receiver data. Given that GNSS faults can cascade to constellation-wide MC faults, this work determines the conditions where GNSS-MC improves integrity, and quantifies this improvement as compared to GNSS only.