There really an awful lot written about this in the QR forum and the Middle-east Airline one, as well as here. I guess T2 will simply be a variation on he established theme.

In essence the back-to-back seems to work as a regular transfer. QR's Cairo team must be used to dealing with this, and liaising with the immigration police. The transfer is irregular in that it doesn't fulfil the usual definition, which would involve a third airport/destination/country, but this doesn't seem to be a concern.