There is no export of OBS that I am aware of.
If you do not want to XOG out OBS's ( that will givethe units and associations as well) you can create a portlet and export to excel.
If you do no have that many you can create a dynamic lookup with
SELECT id
,unique_name
,name
,description
,obs_type_code from prj_obs_types
and copy the results from the preview.