Oh nice to know the thing about the SIM cards! Regarding your question, I recall reading a paper which compared both cases: the office owning the whole infrast

Oh nice to know the thing about the SIM cards! Regarding your question, I recall reading a paper which compared both cases: the office owning the whole infrastructure, and one in which it is rented/outsourced to an established MNO. While the paper suggested that both use-cases are plausible, in practice your preference is likely to vary depending on local regulation and use-case (e.g. latency requirements etc.).