thanks for the hint rocko, and thanks for the read sebastian bacher.
i know that we cant go around making the ntfs drive owned by the user, but changing the fstab line to something like:
/dev/sda2 /c ntfs defaults,umask=007,uid=1000,gid=1000 0 1
gives some useful results at least: 
files are deleted with a single delete key, and appear in trash:// but havent been copied on to the other partition, but are rather stored in the folder .Trash-1000. (if the fstab line is changed back, files in .Trash-1000 do not appear in trash://), so it is all technologically possible

Security concerns dont really exist with trash folders on shared drives:
If you delete a file that was public on an ntfs drive, you expect it to go to your trash, and will expect it to still be public, and if you really want to get rid of it you will know you have to empty your trash. The problem set up in gutsy was where file were deleted and then vanished from the gui, but still existed on the hard drive, ie security worry as people thought it was gone, but it wasnt. As the files are now in the gui there is no problem any more. This is the expected behaviour.

If another user puts a file in your recycle bin maliciously, this can hardly be called a security concern either. The idea of potentially a malicious file appearing in your trash and you opening it is not really something to worry about. The exact same thing could happen in the drive itself, ie a user puts a malicious file in your reservered (ie by social convention) folder on the ntfs drive, and you wonder where it is from and open it. the fact that it is now the trash folder as well adds nothing. 

if each user has a seperate .trash-{user} folder on the ntfs drives, the above concerns only exist if another user on the system goes out of their way to either read someone elses trashed files, or to put a file into someone elses trash folder. But as there is no concept of any security on this drive, this is already the case: a user can go out of their way read someone else's files, or to put something into someone else's reserved (ie by social convention) folder.
by putting an ntfs drive into your computer the users and admin have to accept that there is a potential security hole through this drive, and are relying on trust for your users, the trash is no different

all the technology is there now. the only worry is security concerns, but they are really moot. We cant help people who have ntfs drives, they know that security is weaker. They must accept that any files stored on that partition are going to be public untill they are completely removed (but now are not put under the false impression that they are gone), and also that any other user is free to put any file onto that drive, which you might bump into by accident.

i suggest using .trash-{user}, and having the contents of that folder appear in the relevant user trash:// folder. if the admin cares about security of files it will be obvious that no files should ever be stored on the ntfs drive (or get rid of the drive), if the admin lets the users store file on this drive, then it is clear that the admin is relying on trust between the users when dealing with files on this drive, so the trash system i just described is appropriate, and isnt any more vulnerable to attack or security comprimise.