It can be hard to discern when to grant certain advtrains-related privileges, especially given the lack of protection checks for privileged users, who can then go on to abuse them. The interlocking privilege by default will let players modify TCB information in any area of the world, even ones they can't build in. This, for example, could let the wrong people remove interlocking from a section and cause a denial of service or crash.
This mod will restrict TCBs and some signals (compatibility not guaranteed) to make it only possible to modify them if the user has permission to modify the area. This does mean you may need to operate your server in a different way than you currently do. It may not be suitable in 100% of cases either. For instance, say you have a public railway network and deputies, helpers and so on who are meant to be able to help troubleshoot issues like stuck trains. Those deputies need to be given protected area access to key parts ofthe railway infrastructure so they can do their duties.
Don't worry about locking admins or high-level railway staff out of signals either. The mod at time of review also does not obey the protection_bypass privilege (this is not something the engine does by default, kind of annoyingly), however it does grant access to anyone with the train_admin privilege (which also grants access to place, destroy and drive all trains as defined in the core modpack of AdvTrains.)
Lastly, this mod should hopefully be made obsolete, but the author is quite right in his current comment that it is just not timely to get changes into AdvTrains at the time of writing.