First of all, this statement is wrong:
Your script is indicating both a DC and the Adaxes service when it should be one or the other.
You can use the -AdaxesService and -Server parameters together.
Secondly, your script looks OK and should trigger your Business Rule, but for one occasion. The Business Rule will not be triggered when your script does not modify anything. So, if your script sets all properties of all the users to the same values that they already have, your script won't actually modify anything and will not trigger any Business Rules.
Also, check whether your script is run at all. To check this, have a look at the Activity History of the Scheduled Task.
And finally, since you are running the script from a Scheduled Task, why do use the cmdlets and not ADSI interfaces? With ADSI interfaces, the script will work faster and will be much easier to write.