Is it possible (in CS5.5) to have a paragraph rule bleed to the fore-edge? It's possible to get the effect by setting negative value for the left or right indent. I can then set up separate (heading) styles to achieve that for headings on left and right pages, but if the text shifts or pages are added the headings will need to be redone. Is there some clever way of making this automatic, so that one style will have a rule that always extends to the fore-edge, whether it's on a left-hand or right-hand page?
No. I use in such cases left and right style variations, like H1-left and H1-right based on H1-left. I apply at the end the correct style.
The only way I've been able to do it is by adding in a white bar along the edge it crosses the spine, to cover it. Putting this on the master page on a layer above is a way to achieve this, but not ideal and has it's caveats.