Can A Terrestrial Radio Station Sue Over A Broadcast Callsign?

Last month, I purchased a broadcast callsign and a one-year membership to the National Association of Digital Broadcasters (NAdB), which is authorized by both the Federal Communications Commission and the National Association of Broadcasters to assign digital broadcaster (-DB) callsigns in place of now-obsolete internet radio (-IR) or online radio (-OR) callsigns.

When I purchased the callsign and was assigned the WPMD-DB callsign, I did not even know there was a WPMD callsign in any other format until I did some quick research. There is a WPMD-AM based at Cerritos College in Norwalk, CA.

So my question is:
Should Cerritos College decide to go after a callsign for digital broadcasting (like if they wanted the same callsign; e.g. WPMD-DB), can they legally sue my broadcast media group over the callsign? Or will the NAdB pretty much tell them "you snooze, you lose" (since I purchased the callsign first) and go after a different callsign?

Thought I'd bring this up because a friend told me that an existing AM or FM station could sue over a digital broadcaster callsign, even if they don't own it.

 

I'm guessing yes, the FCC licenses all stations and gives them a callsign.
If your using the same callsign then its impersonation.

 

The FCC authorizes the NAdB to assign all -DB callsigns. All new membership applications include the option to select your own callsign or be assigned a random callsign. I picked WPMD because it made sense that it's an abbreviation for W(W)P(M) M(e)D(iaNet), the name of my Internet radio station.

Of course, all requests have to be sent off to the FCC for approval and they saw no reason to protest the callsign assignment. I received official FCC and NAdB paperwork authorizing the callsign assignment within weeks after application. (I only went after the callsign because stations with a -DB callsign can be listened to on Internet radios, whether it's a home console or one that's installed in a vehicle.)

I'm not impersonating anything - I air completely different programming than WPMD-AM and I don't run a college radio station. If I was impersonating, I would be airing the exact same programming as they are.