82	+    <class
83	+        class="lp.soyuz.model.binarypackagepath.BinaryPackagePath">
84	+        <allow
85	+            interface="lp.soyuz.interfaces.binarypackagepath.IBinaryPackagePathSource"/>
86	+    </class>

No need for this. You already grant it to the securedutility.

104	+    <class
105	+        class="lp.soyuz.model.binarypackagereleasecontents.BinaryPackageReleaseContents">
106	+        <allow
107	+            interface="lp.soyuz.interfaces.binarypackagereleasecontents.IBinaryPackageReleaseContentsSet"/>
108	+    </class>

Same here.

You also have one Source and one Set. Please make them the same.

+    path = TextLine(title=_('Full path name'), required=True, readonly=True)

s/Full path name/Absolute path/, perhaps?

158	+    def getOrCreate(path):
159	+        """Fetch the ID of the given path name, or create it.
160	+
161	+        :param: path: The full path name to query or create.
162	+
163	+        :return: An ID.
164	+        """

Why an ID? Why not the object itself?

191	+    """The contents of a binary package release.
192	+
193	+    A binary package release is a representation of a binary package in
194	+    one or more releases. This class models the files contained within
195	+    the binary package.
196	+    """

In one or more releases? I think replacing all this with a one-liner would be good. "A file contained by an `IBinaryPackageRelease`." or so.

250	+    def getOrCreate(self, path):
251	+        """See `IBinaryPackagePathSource`."""
252	+        store = IMasterStore(BinaryPackagePath)
253	+        bpp = store.find(BinaryPackagePath, BinaryPackagePath.path == path)
254	+        if bpp.count():
255	+            return bpp[0]
256	+        else:
257	+            bpp = BinaryPackagePath()
258	+            bpp.path = path
259	+            return store.add(bpp)

Try something like this:

    bpp = store.find(BinaryPackagePath, BinaryPackagePath.path == path).one()
    if bpp is None:
        bpp = BinaryPackagePath(path)
        store.add(bpp)
    return bpp

314	+        with TempDir() as tmp_dir:

Can you use a TemporaryFile instead? Or even a NamedTemporaryFile, if that doesn't work. Or does DebPackage really want a filename, and care about what it is? Also, might as well break out of the with block as soon as you're done with DebPackage.

324	+                bpp = getUtility(IBinaryPackagePathSource).getOrCreate(
325	+                    unicode(filename))

Objection! unicode() on potentially non-ASCII data == wrong. Probably best to treat it as UTF-8, probably skipping if it's undecodable.

Also, this is going to be pretty slow. You may need to think about optimising it down to a single query eventually.

334	+        results = store.find(
335	+            BinaryPackageReleaseContents,
336	+            BinaryPackageReleaseContents.binarypackagerelease == bpr.id)
337	+        for bprc in results:
338	+            store.remove(bprc)

You can't just call remove() on the resultset?

362	+    def test_get_or_create(self):

Method name style should be preserved here. So, test_getOrCreate.

405	+        deb = open(datadir('pmount_0.9.7-2ubuntu2_amd64.deb'), 'r')
406	+        lfa = self.factory.makeLibraryFileAlias(
407	+            filename='pmount_0.9.7-2ubuntu2_amd64.deb', content=deb.read())
408	+        deb.close()

with looks handy here.

420	+        self.assertEqual(13, results.count())

This is a bit too opaque for my liking.