And undoubtedly ARRL will cite "potential interference" to emergency HF amateur radio communications in its opposition, as they do with all FCC filings. While I consider high speed trading to be a lousy opportunistic/predatory product of end-stage capitalism, there is probably no technically-supported opposition to this use of the shortwave bands, assuming it's unused frequencies and they comply with existing regulations for spurious emissions, human exposure safety, etc. SW broadcast stations have been operating for years in these bands at very high power levels. It's been in such decline that there's only a few pay-to-pray stations left, and of course overseas banana republic stations.
It should be noted that high speed traders have been using licensed Part 101 microwave links in the US for years. I've heard anecdotally that they gut the radios to remove most of the baseband electronics in repeater sites in order to have the minimal amount of propagation time. It makes money for someone but sure seems like a waste of equipment, steel, and radio spectrum, resources that could be used for humankind elsewhere.....
I think you can still buy time on WBCQ, much cheaper than standing up a new station....