With the two pipeline networks with mismatched MOPs, the pressure cannot exceed the pressure of the network with the lowest MOP.
Pressure control = regulator /regulacja ciśnienia is a separate entity.

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This tool clarifies the requirements of Canadian Standards Association (CSA) Z662-03: Oil
and Gas Pipeline Systems, Clause 4.14.1, which states that if a pipeline may be subjected to
pressures greater than its maximum operating pressure (MOP) from any source, there must be both pressure control and overpressure protection for the line. The intent is that if the pressure control were to fail, overpressure protection equipment would prevent the lower MOP pipeline pressure from being exceeded by more than 10 per cent or 35 kilopascals (kPa), whichever is greater. The design must be based on maximum licensed operating pressure, regardless of normal operating pressure.


Overpressure protection may consist of pressure-limiting or pressure-relieving
systems or both, as long as they continuously and automatically protect the pipeline from being pressured above the predetermined value.

https://www.aer.ca/documents/directives/Directive056_Referen...

IMO.