Yes the reference is to occupied bandwidth. All land mobile radios must comply with this regulation in the future. My understanding is that the FCC Rule is effective in January 2011. It is part of an FCC program called "refarming" of land mobile frequencies. (Land moble is a catch-all FCC term for all commercial two-way radios.)

In the future all channels will be made narrower to allow more channels in the same spectrum space. This will result in changes in transmitting frequencies.

Most existing scanners should be able to receive the narrow band transmissions merely by turning up the receiver volume control. However when the new transmitting frequencies are put into service some scanners may have problems separating channels or tuning the new frequencies.

The AAR serves as the frequency coordinator for railroad radio service channels. FCC Rules take precedence over any AAR rules.