A Scheduled Task or Tasks seem to be one of the possible options in this case.
Another option would be to use Custom Commands and Adaxes ADSI provider. The ADSI provider exposes a set of COM Automation objects that can be used to access Adaxes functionality from any language that supports COM, such as VBScript, PowerShell, C++, and .NET languages like VB.NET and C#. If your IDM solution provides a scripting language that can make calls to COM objects, you can create Custom Commands with all actions required to provision a new user, and then execute the commands via the Adaxes ADSI Provider on each new user created by the IDM solution.
For more information on Adaxes ADSI Provider, have a look at the following article from our SDK: http://www.adaxes.com/sdk/?WritingAdsiScripts.html. In this article, you will find information on how to execute a Custom Command on an AD object using PowerShell: http://www.adaxes.com/sdk/?SampleScript ... mands.html.