Thanks for your replies.
I thought that the state of the index is stored in sys.dm_db_index_physical_stats.
Just by querying it one can get the fragmentation level. This would imply that there is no need for maintenance plan to do some additional checks except to get the numbers from sys.dm_db_index_physical_stats.
My script uses this query to determine what indexes to rebuild
SELECT object_id AS objectid,OBJECT_NAME(object_id) as name, index_id AS indexid, partition_number AS partitionnum, avg_fragmentation_in_percent AS frag,fragment_count, page_count
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL , NULL, 'LIMITED')
WHERE avg_fragmentation_in_percent > 20.0 And page_count>1000
For the tables with avg_fragmentation_in_percent > 5.0 and < 20 the script reorganises the indexes.
One would have thought that with these new parameters on the maintenance plan the same can be achieved.
My results until now show that the maintenance plan ignores these parameters and rebuilds all indexes, regardless what parameters are set.