prefix aggregation

Hi, In many places yet we're discussing prefix aggregation for at least 193/8, 194/8 and 195/8 IP blocks. I was told since a while that some US carriers -such as SprintLink- have decided to filter (id. no more route) prefixes longer than /19. My questions is : - is this impleted yet ? - if yes, who does it, for which class(es) of prefixes of which length ? - if no, when do you intend to have this filtering operational ? As I'm acting as a "consultant" for the french academic network (Renater) I'm interesting in knowing what policy every ISP -specially in the US of A- intend to implement in the near future. Thanks for your help and time, Regards, +Bernard Tuy.