What is the official allocation in 27.5-28MHz anymore? For a while
there were commercial users but I don't know if they're still around.

The last time I looked, the official allocation was aviation. There
may be secondary users though...Saying that, I've never heard
an aircraft using that band. Actually...I don't believe I've ever heard
anyone using that band except CBers, but I never really listened
too awful hard. Biz users are probably fairly recent I bet.. I've
heard quite a few of those on the low VHF band when it's opened
up.
MK