It is a good question , some people put maintain army in
another sphere , but I noticed rading the book of
priestcraft that there is a spell for nearly all the sphere
of priest magic , perhaps TSR wanted to give an even access
to spell , and not all spells that includes war like
maintain army and so on as war , otherwise all the other
sphere would seem a bit pointless.

But my ruling is that only major access sphere can be used
to cast realm spells , because you need the full acess to
cast such powerfull magic.

Ciao

Giovanni Garzelli