Considerable divergences from normal usage" and "special applications" mean that the subscription is being used for a purpose other than intended (i.e. not of that of a normal mobile connection) or is being misused.
Examples:
Surveillance applications with video, photo, voice or webcams
Use of the SIM in a gateway, router, WiFi hotspot device, USB modem
Machine-to-machine connections such as in vending machines, for home monitoring, etc.
Use as a gateway
Direct dial and continuous connections, leased lines
Purely stationary usage
Usage behaviour that makes such intensive demands on the available network capacity that the latter is severely compromised for the remaining customers.