Tested on Ubuntu 9.04 with the bundled openoffice version, using writer and calc:

If I don't have write access to a file according to standard unix permissions,
but I do have write access according to additionnal posix ACLs, OpenOffice will
not allow me to edit the file, ignoring the ACLs.

Note: strangely, if the unix permissions don't even allow me to read the file
(chmod o-r), then I CAN edit it. (!!)

EXAMPLE CASE:
I am user sduchesneau, I am NOT in the group "share"

I cannot edit the following file:
# file: Document.doc
# owner: share
# group: share
user::rw-
user:sduchesneau:rwx
group::rwx
mask::rwx
other::r--

but I CAN edit the following file:

# file: Document.doc
# owner: share
# group: share
user::rw-
user:sduchesneau:rwx
group::rwx
mask::rwx
other::---

I SHOULD be able to edit both, since my user can modify the files on the disk.

If I put sduchesneau in the "share" group, of course, I can edit the file.