Hi Angie,
Thanks for the further clarification, it helps! Now I know its a reprint of the 1991 original map. So, yes, DtSt r and 2019, 1991 as you have it. I would use the existing name of the company in 264$b and add a note of explanation about the name change. IF there is an authority record for the new company it should have data to reflect both relationships, from old to new name and also new to old. My guess (nope, I did not go search) is that the new company name has not been established and so a quick note in the record may be useful to another cataloger, your users, and potentially helpful to whomever creates that authority record (again, assuming is has not been created yet).
Paige
Angie,
At least you know the details of what transpired! Good idea to reach out. In the meantime, one of RDA's primary principles is "take what you see". Follow what is on the map, but if you have to use the website for date details you can do that too but provide the data using square brackets.
I assume you are cataloging the new 2019 map? If so, is there an edition statement? If not, no worries, if the 2019 date is available use it, whether it is given as a publication date, copyright date or whatever. I think it would be safe to also use 2019 as date of situation in the call number if the evidence is there. Again, you heard from the owner of the map so if you have to you can reach out again and ask if data on the map has changed (I would be shocked if it has not given the number of years between 1991 and now).
Suggestion: I would not put the copyright statement in 245$c, this can be given as a quoted note. I don't remember a specific rule but I do think there is/was a rule interpretation for this in AACR2 and it is also "practice" to not consider copyright statements like this as true statements of responsibility even though it infers so.
As for publisher, City Maps Illustrated Pty. Ltd.
Paige