This seems difficult, either the information is there (in the IPTC) or not. In MediaPro it is probably hidden, and maybe there is a setting to inactivate the writing of certain IPTC fields when converting/copying to JPG?
Many programs (including simple and free viewers like Irfanview) offer to delete Exif and/or IPTC in JPG. I have not seen any that offers selective transfer of specific IPTC fields.
I write IPTC to the raw (NEF and RW2) with PM5 and convert to jpg with ASP (Corel AftershotPro). I have settings to convert to "normal" JPG which retain IPTC, and to reduced JPGs with no IPTC. Adobe does the same when using "output for web" => Exif and IPTC are stripped.
It is certainly doable in PM if "they" decide to do it. I would not use it since I only ingest Raw with PM, I think the selection (full or partial IPTC) is more useful for the final JPG.
Francis