They did, IIRC back in the late 00s they were also paying IBM to port software to HP-UX on Itanium, because I remember I was given a machine to play with and was asked to produce builds of some components.

From what I remember the only drama was that there was a missing pthread_ API implementation on the platform, might have been pthread_gettime or something.

Compared to the HP-UX on PA-RISC box I had access to at the time, the performance was amazing!