Sketchup.active_model.pages returns a list of the SKP's scenes.
pages["Scene 1"] returns the scene with that name
pages[1] returns the second scene etc
This list is in the order the tabs are displayed.
You can set_current/add/erase pages etc so you can manipulate the list...
pages.add(name,flags,location) adds a scene [or replaces the scene at 'location' - e.g. 1 for the second scene - if no 'location' is given a new page is added at the start].
The bitwise 'flags' is also optional - it represents the scene's properties - http://code.google.com/apis/sketchup/docs/ourdoc/page.html#update explains this...
So it would be possible to write a script to reorganize scene tabs...
BUT it's complex.
Smustard.com has several 'page' tools [some free, some inexpensive] that might help you.
One way would be to use the scene [page] export method [provided by 'pageExIm.rb' - $5], then sort the lines in the .sup file that's generated [with Notepad++ etc], then erase all scene tabs and immediately reimport the scenes in that new order as desired, using their names ?
Tip: this tool might cause problems if you haven't [temporarily] reset your Model Info > Units to 'inches' when doing the 'export' - it exports details in current units, but then imports assuming they are in inches - at least in the [perhaps older] version I have [that I have adjust to automate this temp-units issue to always export/import in inches irrespective of current-unit settings]...
There are also a Smustard tool to rename scenes logically after reordering if needed...