Mobile networks for telephony and the Internet are far less reliable than their fixed systems counterparts. Mobile incidents occur far more often and affect many more users than those of fixed systems. If a mobile provider’s service fails, service from one or more of another provider could temporarily accept traffic of customers from the downed service. About 1.75 million mobile users were without service for each incident last year compared with about 350,000 for fixed users, according to the ENISA annual incident report. “Technically, it’s possible; it’s not rocket science to do this,” says an ENISA network and information security expert.”]
Source: https://www.careersinfosecurity.com/employing-roaming-as-backup-to-mobile-networks-a-6019