From c.l.p: in response to glitch report, 2nd person showed that it is specific to __pow__

>>> class MyInt(int):
...     __sub__ = int.__add__
# similar lines for 9 other methods omitted
...     __or__ = int.__add__
...     __pow__ = int.__add__
...
>>> i = MyInt(42)
>>> i + 3
45
>>> i - 3
45
# similar outputs omitted
>>> i | 3
45
>>> i ** 3
74088

Another person (3rd) confirmed presence in 2.5 
Python 2.5 (r25:51908, Jan 21 2007, 03:10:25)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-3)]