remount /system on rooted Archos 80 g9

On archos g9 there is an ext4 filesystem for /, and no separate filesystem for /system. Tablet is temporary rooted and ics is installed

After adb remount I get something strange like (I am unable to test it now):

Adb remount error: Remount successful
 

When I try to remount "/" from adb shell it doesn't work either. But I really need to put apps to /system/app to test them with system level privelegies (not 3rd party app).
Is there any way to do that on rooted archos g9?

Thanks

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