Unfortunately there is no standard for telemetry sensors, so telemetry sensors for one system will not work on another manufacturers. The exception is, 3rd party sensors, e.g. SM Modelbau, which have been programmed to work on various systems.
So the Jeti MBar sensor won't work with Multiplex MSB, but if you are handy with electronics then Multiplex publish their MSB standard (it's in the downloads section) and you can build your own sensor. Worth checking out the OpenXsensor website for examples.
Also note that with the Multiplex telemetry it is not possible to assign bar or kPa as units so you'd have to select another unit.
Also the Jeti sensor is for measuring air pressure and hydraulic pressure. With a maximum operating temperature of 85 DegC. So i am not sure if it would be damaged if measuring steam pressure if exposed to hot steam.
I do think a pressure sensor would be useful addition to the MPX sensors.