Yes, operating in one of the under used broadcast bands could work very well. 120, 90, 60, 22, 19, 16, 15, 13, and 11 meters all have lots of clear frequencies. 120, 90, 16, 13, and 11 meters are almost completely vacant of stations. I think the 49 meter band is a bit too crowded to pirate on. The pirates I have heard in the 49 meter band all suffered severe interference from legal broadcast stations. I don’t think the raided stations were operating on frequencies used by anything else. They both operated in the 43 meter American pirate band. The only legal transmissions I have heard there are MARS stations and the link-11 data on 6945 LSB. The usual 48 meter Europirate band is an HF marine band so it would make sense for a station operating there to get caught for using an emergency channel. In my opinion the 48 meter band is a poor choice for Pirate activity. The last place you want to pirate is on or near safety of life frequencies but many Europirates do. I still have no idea what they could have been interfering with in the 43 meter band though.
I don't know the original post "Comreg Raids against SW stations in Ireland", what station was raided ? what frequency they used ?
Be careful that - in Europe - low band such as 120m, 90m or 60m are not in use by station BC but are in use by digital operators, maritime services etc...
For example 2177 khz & 2187.5 khz - 120m BC band - have the same usage as 6312 khz.
https://www.govinfo.gov/content/pkg/CFR-2003-title47-vol5/xml/CFR-2003-title47-vol5-sec80-1077.xml