Hmmmmmm...

Sounds to me like the Communications Dept hasn't heard of
TEAMwork; nor understands the concept of "moving" the experienced
Employee WITH the Job.

I'd go back to YOUR Boss and ask her if she could arrange a
meeting with the Head Of Comms, herself, and You.
Purpose being:
Ask Boss to "explain" the not-so-obvious fact that YOU are already
DOING the job that Comms has just advertised for... and
The Curtious thing to do is for Comms to Interview YOU for a TRANSFER
to their Dept (along with the Work You're DOING) -
"before" they advertise for a new employee.

I'd also "wonder" if "someone" isn't already waiting in the wings
for the "new" job in the Comm Dept.

Sounds like a raw deal for you!
I'd ask your Boss for some more Help in resolving this - ASAP.

WE're all with ya 110% - but we don't sign you paycheck.

Try to keep a clear head and focus on finding a Happie Solution.

BIG {{{HUGS}}}, Kimmy!!

/s/ Phre