The answer is obviously, Yes, You Can. :)
If you disable this third party extension either via editing code or via admin, then magento will start to use its default helper/Model class. Yes Magento is smart enough to to do that.
In order to disable this extension via admin, you need to go
System > Configuration > Advanced
In order to disable via xml file, you need to find activation file of the extension. Most probably it's name would be
Kadro_PIO.xml. So go to
app\etc\modules\Kadro_PIO.xml and then change
From your comment, it seems that, the extension do other jobs for you. So my solution will not help you, since it disable that extension fully.
If you just need to avoid the rewrite part, then the fastest and easiest way will be comment out that rewrite part in the extension's
But this is not the proper way to do this. If you need to do this in clear way, then I will suggest you to create a small custom module that will rewrite the extension's rewrite model file.
For this your module
config.xml should holds this part
class Namespace_Modulename_Model_Product_Image extends Kadro_PIO_Model_Product_Image
//here you can overwrite any method that extension uses