How did I miss this until now? It's great that WSSv3 and MOSS give us granular permissions, and it's great that I can access those permissions via an SPListItem's RoleAssignments collection - but is there really no way of getting this information in a web service?
The Permissions web service remains unchanged from WSSv2, GetPermissionCollection() receiving a List GUID and returning permissions for that list. Nothing for specific documents. Interestingly enough, the method also receives an objectType string, which could ostensibly allow us to pass other types of objects and get permissions data for them - but this apparently never made the cut for WSSv3 RTM.
This, for me, is a major roadblock. I am limited to accessing the built-in web-services only. I don't have access to the Sharepoint server(s), and can't write my own web-services to expose this data via the object model.
Has anyone ran into this and found a more imaginative workaround for this really painful oversight?