Please find the answers to your questions in blue below:
My understanding till now was, that all kind of paper invoices will be removed latest one year after SIS going live.
I assume you are referring to the Passenger and Cargo mandate date, which is indeed September 2012. From that date on, old IDEC will be discontinued and Passenger and Cargo must be billed via SIS. Hence – there will not be paper anymore.
Check in the RAM it says the following:
RAM 2011 (SIS version) – A9 3.3.
(e) Three months after migration to SIS the billing carrier can stop sending paper copies of their invoices and supporting document to the billed carrier. The billed carrier must download or print copies of the invoices issued by the billing carrier using the appropriate SIS facility.
This is a RAM rule for a migrated billing carrier to provide the paper invoice-listing-memos for 3 months after migrating.
Carriers on a bilateral and multilateral basis can supersede this rule (and most probably will do so).
Without all airlines joining SIS this will never work, or? And also on project kick off meeting (as far as I can remember) it was said that all airlines will have to join SIS, otherwise migrated carriers will have less benefit of SIS project. The whole procedure will not work if a carrier which I will or who will bill me is not member of SIS.
As mentioned above, SIS is mandated and not optional. So all participants will have to join SIS if they want to settle with ICH or ACH.
Note: SIS also allows bilateral settled transactions.