I've been looking at the 'Application Initialization' module for IIS 7.5 (which is baked in to IIS 8) and serviceAutoStartProviders which can be set to initialize services when an app loads up.
I'm wondering what happens to serviceAutoStartProviders when an app has AppOffline.aspx, to bring down the app for whatever reason. Do the providers still run, or no? In my case, I have a provider that I would not want to run while the app is being updated - and I use AppOffline.aspx while I'm updating the app.
A quick test, it appears that serviceAutoStartProviders do run even if App_Offline.htm is found in the application directory.