Theoretically possible. Using current off the shelf tech, several imsi catchers could be networked together by normal LTE data networks with battle tested VPN crypto. Doable with any mifi type hotspot device or even just a modern phone and tethering. People with high end spectrum analyzers and directional antennas would struggle to locate a thing that only powers on for 1-2 minutes, and the relocated to a random location. If I were trying to find such things I would need three separate DF (direction finding) teams, and try to establish a pattern of behavior or movement on the part of the operators to narrow down the target areas. Could take weeks.