Yes.
My answer is based upon the specifications sheet here
http://www.shop.bt.com/content/uni2/documentation/9m2m/bt8500_spec.pdf
which says "Associated ring tones: Yes"
. . . and upon reading page 11 of the set-up guide which indicates that you can assign a particular ring tone to an individual contact, which will work irrespective of whether they call from their home, work or mobile number:
http://www.shop.bt.com/content/uni2/documentation/9m2m/bt8500_quick_start_guide.pdf