To check rules synchronization I did the following:
a) created new file from new default.ect (thank you for it)
b) created its synchronized copy
c) and played with the original file and its sync_copy just by opening and closing them in turn under ecco32 or eccoext.
 
 
It seems that a rule synchronization depends on where a rule had been  created (or edited).
 
Rules created under ecco32 sync when the sync_copy is opened either with ecco32 or eccoext.
 
Rules created under eccoext do not sync either with ecco32 or eccoext.
 
Besides, for a traditional rule to be functional it needs to be created under ecco32, i.e. a traditional rule created under eccoext does not function (yes, the option Enable Traditional Rules is checked).
 
Eccoext 4.0.0.1 under XP

This bug is very annoying for us as I am frequently modifying the scripts and the synced copy is not updated.
However, I found a workaround: Open the file with the LUA rules in std. Ecco instead.  
Then simply click "Auto Assign Rules..." to open the dialog box. Close it again w/o doing anything.  
Now the rule is synced with the the other copy (running EccoExt).
 
 
BTW, why is a "0" added when looking at the rule in std Ecco??
For example:
++:L:-- test     (as entered in EccoExt)
++0:L: -- test   (when looking at the rule in std Ecco).
 
Is it safe to remove the "0"?