You certainly can lubricate phosphor bronze bushes.
Phosphor bronze is generally chosen as a bearing material in high load applications where corrosion and or difficulty in lubrication are present.
There are many types and grades of 'self lubricating' bronze bushes, oil impregnated, carbon plug impregnated etc.
I would guess that the bearings in the roof are oil impregnated which means essentially that they are 'oiled' and this oil is released as the bearing is subject to rotation. Adding a drop of thin oil wont harm at all just avoid EP oils as they have additives that copper does not like and copper may be in the bearing....
On my 23i the roof was deathly slow so i half opened the roof to inspect the pivot points. Some of them had rust staining around the bearings and the staining had run into the bearing. So, i covered the interior and WD40 sprayed the joints. I left it for a couple of hours, dried it then treated it with an aerosol white lithium grease.
The difference in roof smoothness/speed was very noticeable..