Until 1928, portable radio stations were permitted. The idea flies in the face of everything you currently know about radio. Today the notion of even a class A radio station moving from city to city invokes images of chaos, RF interference, noise, human sacrifice, dogs and cats living together in harmony, mass hysteria... But before 1928 that was a genuine part of the radio landscape.
In 1923, the Edison Electric Company in Boston started using a portable radio station to market electric appliances. WTAT-AM first broadcast from Dedham,
MA out of an REO Speedwagon. They pushed home electrification and of course radios. Later the same station used the calls WATT-AM. Also in the Boston area was WCBR. Charles Messter signed on WCBR-AM operating at 5 watts on 1220 kc. He touring his station around new England frequenting fairs and amusement parks often with
local politicians as guests starting in 1924. By 1925 he was operating at 50 watts as far north as Portland, ME before he quit in 1926. More here.
Zenith, the radio manufacturer launched WSAX-AM, it's first portable station in 1923. It's 20 watt transmitter was licensed to the city of Chicago, but it spent most of it's time touring the country and trying to sell more Zenith Radios. In 1926 they built a 100 watt transmitter and caused even more of a ruckus. Later they transferred the 1120 Mhz frequency to their land station WJAZ. But Zenith was far from the worst offender. (The book The Beginning of Broadcast Regulation in the Twentieth Century by Marvin Bensman goes into this in detail.)
Carrell seems to have left most of his wherever they were parked that day. He demanded and got a hearing with the FRC and was rebuffed curtly. His WBBZ transmitter stayed in Ponca City, OK and WHBL stayed parked in
Sheboygan, WI. WHBM put down roots in East St. Louis where it had only just arrived. Edison Electric dumped WATT and launched WEEI. Charles Messter presumably moved on to new hobbies.