If you export to Ris the page information is not included (in the OPAC) i also tested bibtex same problem i did a test by exporting all the koha marc fields to RIS (filled them all up with a number) and then importing the ris file in endnote the page information was not transfered ... the page information in endnote stayed empty (the marc field i use is 300 a checked library off congress they use the same field)
This is still valid for RIS at least. It might require some "clever" guessing as the page information is stored in a non-structured way in 773$g (also: mutli-lingual: German S., English p.) and RIS expects start (SP) and end page (EP) in separate lines. I consider this a bug and not an enhancement as the information is vital for articles.