Not artificial. There are a few reasons:
1. Anne Arundel is part of Baltimore Council of Governments (COG), and Montgomery is part of the Metropolitan Washington COG. There would have to be a special MOU between them for regular responses.
2. Because of the infrequency that the two might interoperate, they do not share communications capability other than NPSPAC channels.
3. The two jurisdictions have very little experience in working together, which could cause unnecessary confusion on the fireground. Working with the border counties more often decreases this likelyhood.
Not to be argumentative, but here I go
1) An MOU is just that; nothing mystical about it. True that Montgomery is part of the MWCOG, and AA is part of the Baltimore COG, but I would suggest that it's more of a cultural separation between the two regions than the membership of two different councils (like Skins vs. Ravens, O's vs. Nats.) Being members of different organizations and/or MSAs is not a valid excuse not to cooperate when logical / practical. Montgomery and Howard counties run mutual aid, and they are not in the same COG.
2) How hard is it to include Montgomery's EOC's number on speed dial, or vice versa? It's not, and it probably already is - it just getting people used to the idea that the jurisdictions are not that far apart. A few meetings, follow-up training could settle the issue, and the new equipment that both jurisdictions will be buying is certainly capable of supporting enhanced cooperation (radio and CAD.)
3) I grant you this, but we all take the MFRI courses (or equivalents) and the MIEMSS EMT / advanced courses. SOPs do vary of course - particularly on the fire side - but nothing insurmountable (SOPs vary between volunteer departments within Montgomery County.)