The regs are pretty clear...
When they say regularly maintained, do they mean maintained by the government or maintained by anyone??
By anyone (who has the right to maintain it - try driving a grader down a road allowance that is overgrown and see if anyone comes at mach-chicken once you are noticed).
Most likely. Read Kev's post.
The statement applies to all roads EXCEPT those under a PLA disposition. Most oilfield roads fall into this category, so you are generally allowed to shoot from them. However, when a company applies for this disposition, the Gov't MAY tell them they must install access control features, and can in fact, place further prohibitions on at the time of disposition issuance. So, if there is a sign telling you shooting is prohibited, there is a good chance it has legal backing.
Permission to build a road on Crown land usually comes with stipulations saying you must restrict access, and may contain other requirements the company must meet (or else the government can fine them, deny further permits, or revoke the permit for the road in question).
Just because it's Crown land doesn't mean you can go on it. Try going into the Siffleur or Whitegoat and find out how much 'right' you have to go running around doing whatever you like on Crown land...
Don't like it? Vote someone else in then or get the people we have to make hunting, trapping and fishing a priority for land-use management under law.
Really want to know the answer?
Phone the RITE line (toll-free) and get connected to the Lands office in your area.
Have the legal land location of the road handy.
Have details of the sign available.
Get the name and job title of the person to whom you are speaking and write it down along with the answer (when you get a call back from the person who actually knows).
Remember, the government employee to whom you speak is there to serve you and the rest of the citizens of Alberta, but probably won't appreciate being told that they work for you.