I've heard about the 27.555 MHz USB jammers in Europe and the UK as well. I've never actually heard them myself during band openings to Europe, even when the band is very open to the UK/Ireland area and I can hear UK FM CB activity (and even work UK stations on the UK FM channels when the band is really open!)
26.285 MHz USB is certainly an option for alternate calling frequency. 26 MHz is popular in Poland and elsewhere. Here in the Americas, 26.555 MHz LSB, 26.225 MHz USB, 26.230 MHz USB, 26.235 MHz USB and 26.500 MHz LSB are popular SSB calling frequencies for Spanish speaking stations on 26 MHz. There are numerous 27 MHz SSB calling frequencies for Spanish speaking stations, 27.455 MHz USB being the big one.
26.285 MHz is channel 19 "down two bands" (see also: 26.735 MHz, 27.635 MHz and 25.835 MHz). In the US, it is common for trucking companies, logging companies, etc. to use 6-band export radios and flip the band switch up and down from channel 19 to access a "clear channel" or even a "company channel". I have heard trucking company chatter on 25.835 MHz, 26.285 MHz, 26.735 MHz and 27.635 MHz when the band is open, all in AM mode. There appears to be a local or local-ish logging company that uses 25.835 MHz (channel 19 on Band A) for truck-to-truck comms as well. The lower channels upper part of the 25 MHz band and the 26 MHz band is also popular with hunting clubs and other users in the USA and taxi cab dispatchers in Latin America. I know that European 11m operators have had to deal with the QRM from Russian taxi dispatchers when the band is open, Americans have similar issues with Latin American taxis. The Spanish speaking taxi dispatchers almost exclusively use AM mode though, compared to the FM mode used by the Russians.
Other than that, 26.285 USB could certainly be used. 27.555 USB is just a lot more well-known, especially in the USA. Same with 27.385 LSB.