Currently, when generating the autoload array, the class FQN doesn't have escaped backslashes.
It does work this way, but this is not the right way to go.

For instance, with such class :

namespace foo\bar;

class Test
{
}

You will have in ezp_extension.php :

'foo\bar\Test'                             => 'extension/test/classes/testclass.php',

Here backslashes should be escaped.