I registered a plugin to handle import-functionality. Therefore I registered steps to listen to nearly all available import-messages ('Import', 'ImportAll', 'ImportCompressedAll', 'ImportWithProgress', 'ImportCompressedWithProgress') and I also tried every avaialable pipeline-stage (pre-validation, pre-operation, post-operation). It seems, the plugin is never triggered. Neither on data-import nor on solution-import.
Are these import-messages really supported and does anyone ever succeeded in registering a plugin on those messages?