LoA (Letter of Authorization) for Prefix Filter Modification?

["Rodriguez, Mauricio" <Mauricio.Rodriguez () fpl com>]

Recently, one of our Transit providers has started requiring a Letter of Authorization for addition of any of our own 
Transit customers' prefixes to their filters.  The verbiage of the LoA basically states that the owner of the 
assignment or allocation (not necessarily our customer) allows us to advertise their prefixes through our service.

Is this a common practice?  Our past experience indicates that a simple request to a NOC or update of a routing 
registry usually is sufficient.

Regards,
Mauricio Rodriguez
FPL Fibernet, LLC