I get what you're saying, but I keep trying to bend my head around it and my thoughts end up going down one of two separate tracks here and I end up not reaching a conclusion:
1. The bus is a public space - in which case, there's no reasonable expectation of privacy in public (which is well established), and therefore recording should be both legal and protected under the First Amendment.
2. The bus is a private space open to the public - in which case, the owner or the operator of the private space should have the right to record on his/her/their property.
Honestly though, whatever the legal arguments, it FEELS wrong.
1. You're using "no privacy" to mean both "overheard by the grandma in the next row" and "recorded by a centralized mass surveillance system to be analyzed and correlated with the millions of other data points it has on your and your social circle, wholly subservient to the ever-changing will of the state".
So are the courts. By some twisted logic, they concluded that because you can't expect that a random passer-by hears you, you have no reasonable expectation that everywhere in public isn't infested with microphones and cameras uploading everything to intelligence agencies or corporate headquarters.
2. We should be careful, as ever more spaces are becoming "private, open to the public". Perhaps most notably the parks in Wall Street. Soon we may have to travel out of city bounds for any meaningful privacy, if that isn't already the case.
1. The bus is a public space - in which case, there's no reasonable expectation of privacy in public (which is well established), and therefore recording should be both legal and protected under the First Amendment.
2. The bus is a private space open to the public - in which case, the owner or the operator of the private space should have the right to record on his/her/their property.
Honestly though, whatever the legal arguments, it FEELS wrong.