KBOO's signal, centered at 90.7, starts at 90.5 MHz. The edge of the digital HD signal touches 90.500 MHz. By a pirate operating on 90.5, half of the pirate analog signal is directly over the KBOO signal.
KBOO did not purchase spectrum as they are a noncommercial station, and those stations are not subject to application or regulatory fees. KBOO has the same rights to the 200 kHz for analog and the additional digital bandwidth on either side, as any licensed FM station in the US has (expect for perhaps some FM translators).
As for analog vs. analog on adjacent frequencies, they interfere with each other, because there's a little bit of overlap. Analog signals don't have that "cliff" that the band edge that digital signals have. Analog FM can fit right next to digital, because the digital signal stops right at the edge. But the little bit of overlap of a 101.3 signal onto 101.5 is doubled when you consider the little bit of overlap from 101.5 to 101.3. It's significant interference on a receiver.
If you look at the lineup of licensed stations in any one location, you'll notice that stations are spaced by at least one vacant channel. For example, in most cities you'll see an alignment like this: 101.3 (full power), 101.7 (low power or distant), 102.1 (full power), 102.5 (low power or distant).
A full power station can't be in the same vicinity as another full power station for 3 adjacent channels. That is probably overkill, as it's made with consideration for receivers made decades ago that are no longer in use.