Yes! I just managed to use opencv-2.4.8.exe from within WinPython-32bit-2.7.6.3.exe.

For this, I followed this description:
I copied opencv\build\python\x86\2.7\cv2.pyd to WinPython-32bit-2.7.6.3\python-2.7.6\Lib\site-packages\, then opened Spyder and tested import cv2.

So this ticket can be closed.