It varies, a lot, and depends upon a lot of things. I'm not current on all the current details, but many moons ago was involved in push notification development.
* Notification path. IoS at the time was pretty protective of the user's battery, and had specific services you had to use. I imagine there's special treatment now for emergency communications.
* Phone state. How deeply asleep is it? Are there other background apps frequently contacting the mothership? Multiple apps can get their requests batched together, so as to minimize phone wake-ups. You can also benefit from greedy apps--VoIP apps, for example, might be allowed/figured out a hack to allow frequent check-ins, and the other apps might see a latency benefit.
* Garbage carriers. Hopefully emergency alerts have a separate path, but I've noticed my provider (who shall remain nameless but is a three-letter acronym with an ampersand in the middle) sometimes delays SMS messages by tens of minutes. (TBF, in my case there might also be a phone problem [Android], but since nameless provider forced it on me when they went 4G-only they're still getting the blame.)
In your case, my money would be on the carrier. Pushing a notification to all phones in an area can be taxing, and cheaping out on infrastructure is very much a thing.
For docs, your best bet would be to go to the developer sites and pull up the "thou shalt..." rules, particularly regarding network activity, push notification, and permitted background activities. And yeah, Apple was much more dictatorial, for good reasons.
I believe they did announce that, and also claim that the letters no longer mean anything (which makes sense as telegraph is long dead, and the telephone network is primarily spam), however their website including investor relations has the ampersand everywhere, so maybe they backpedaled.
Or maybe ampersand was dropped before SBC bought the remaining parts of the old business and reformed T-1000 with the ampersand?
I thought that was when they dropped the ampersand when the biggest baby bell bought the remain baby bells to reform the mothership but couldn't use the ampersand since that was the entity that got broken up in the first place. You can't be too obvious about it and flaunt it in everyone's face. Subtlety is an art. And that art is clearly lost on the FTC
* Notification path. IoS at the time was pretty protective of the user's battery, and had specific services you had to use. I imagine there's special treatment now for emergency communications.
* Phone state. How deeply asleep is it? Are there other background apps frequently contacting the mothership? Multiple apps can get their requests batched together, so as to minimize phone wake-ups. You can also benefit from greedy apps--VoIP apps, for example, might be allowed/figured out a hack to allow frequent check-ins, and the other apps might see a latency benefit.
* Garbage carriers. Hopefully emergency alerts have a separate path, but I've noticed my provider (who shall remain nameless but is a three-letter acronym with an ampersand in the middle) sometimes delays SMS messages by tens of minutes. (TBF, in my case there might also be a phone problem [Android], but since nameless provider forced it on me when they went 4G-only they're still getting the blame.)
In your case, my money would be on the carrier. Pushing a notification to all phones in an area can be taxing, and cheaping out on infrastructure is very much a thing.
For docs, your best bet would be to go to the developer sites and pull up the "thou shalt..." rules, particularly regarding network activity, push notification, and permitted background activities. And yeah, Apple was much more dictatorial, for good reasons.