Unfortunately, it is not possible to provide the IP addresses of the Mobile nodes.
Because of the way the mobile nodes access the mobile networks, the IP addresses are usually generated through DHCP (Dynamic Host Configuration Protocol). In other words, the external IP addresses are dynamically generated, not static, so no list of IPs is available.
You do, however have access to some details of the mobile nodes, in the Mobile Locations tab of the Measurement Locations page in the Dynatrace Portal. See Mobile Locations for more information.