I just found the same thing, found here
(providentliving.org) and here
(FM guidelines, page 3 - this version does not mention the standard plans committee).
The part about the radios themselves is understandable - radios are expensive, subject to loss/theft/damage, might not be properly maintained and there is a risk that non-licensed persons might think "oh, that doesn't look too hard" and do things they oughtn't. The antennas, however, are a different matter and I wish they would reconsider.
1. A permanently mounted antenna can have better performance than a portable one. This has to be one of the first considerations. A properly mounted and tuned fixed antenna can be placed higher up than portable ones which is an important variable in regional simplex operations.
2. A permanently mounted antenna means less setup time and establishing communications more quickly.
3. A PMA provides bus insurance - if the only person who has a portable antenna gets hit by a bus just before an emergency (or in the middle of the emergency) then the ward/stake is out of luck.
4. A PMA is safer for the communications team. Standing around outside a building with hundreds to thousands of dollars of expensive-looking antennas during a week/month long emergency is going to attract unwanted attention. It is safer by far if they could be inside the building. As an added bonus it will probably be warmer and drier inside than out, and you won't have to prop open doors/windows to feed antenna cables through (leaving opening for temperature to move and bugs to get in.
5. A PMA means there is a pre-set, designated location for the radio operators that can't be usurped at the last moment by somebody who, for no particular reason, wants their space. This makes planning and implementation easier and is one less decision that needs to be made.
6. PMAs can easily be concealed - you can get an HF, VHF and UHF antenna inside a flagpole, completely invisible to the naked eye. Run some line to a designated radio spot inside the building and leave the antenna connectors there so people can bring in their radios and test or respond with ease. Ditto with attic mounts, gutter mounts or a crank tower.
7. In an emergency with the chaos going around there is a risk that somebody in their rush to get on the air might be hurt as they climb and deploy. Less likely in rural areas where you have limitless options, more likely in urban areas where space is at a premium and surrounding buildings/interference require you to climb to get any sort of acceptable rx/tx.
8. In the above-mentioned urban areas, a PMA lets you design and deploy the optimal antenna solution for your specific location.