It's not SaaS, it's a software solution running on Intel PC/servers. You plug a (high end) SDR or remote radio head system to feed the PC with the samples, and the rest is pure software. They sell the software. Other companies build on top to sell more complete solutions.

It's becoming quite common at companies involved cellular, as you can have a 4G/5G "network in a box" for relatively cheap and it's very useful for a first pass of testing before going in the field on a "real" network.