Q: Can operator SIM cards with PLMNs such as 23488, 23455, 99999, or 23588 connect to a private network using PLMN 00101, or do I need to change the PLMN on the network?

A: Yes, they can connect without changing the private network PLMN, provided roaming is configured correctly.

A typical setup is to keep PLMN 00101 on the core network and on the gNB/eNB, while provisioning the SIM subscriber in the core with its original IMSI and allowing roaming. In that case, the phone can attach to the 00101 network as a roaming subscriber.

If you choose not to use roaming, then you need to change the PLMN consistently on both the core network and the gNB/eNB. Changing it only on one side is not enough and will lead to registration problems.

So the practical answer is simple: if roaming is supported in your setup, you do not need to reset the network PLMN. If you do want to change the PLMN, do it at least on both the core and radio side, and make sure the subscriber provisioning remains consistent.