Hello, David
to the OB.
I'm not completely sure but i'd say they can be crossed. Most Vandaceous plants are in the Sarcanthinea subtribe, as such they can interbred in most cases.
The problem would be that: the pollen would get rejected often because they ARE in different genera that aren't exceedingly close in terms of genes & location
IF the pod does form theres a very good chance they'll be low viability &
the offspring would almost certainly be sterile
Calvin rises a good point... sedirea's aren't exactly old stand-by's in the western growing scene.
But i think they're is/will be Phal x Sedirea hybrids
If not i intend to make some of my own