After perusing some old NALS seed exchange lists it appears they are generally fertile both ways with trumpet and other aurelian lilies.
The lists are found here with previous years in the lower left corner:
http://www.lilies.org/nals-2/s...
These are pdfs and you can use your pdf "Find" function to search for lily names in the lists and explore how they were used in a cross.
Hope this is of assistance to you.
