I am not certain that this is an IoT question.
I have the impression that those tracking devices would not get any GPS
signal in shipping containers, trucks or buildings, where they would
be most of the time.
Also, I see the same issue regarding the connection to a cellular
network or alike, especially in regions with bad network coverage.
I have developed tracking systems, and can tell you the following - for package tracking, you do not get the current location.
You package is tracked at "gateways" along its delivery route. It is collected or handed over to the shipper, then it goes to a depot, from there, possibly, to an airport or ship, reaches a destination (air)port, gets loaded onto another truck, goes to another depot, onto a another truck, and heads towards you ...
... but, at every step along the way, it is scanned & updates the database which provide you with tracking info. You are NOT (currently, this year, or any time soon), going to see "it is on the high street; it just passed the crossroads; it is turning into your street; your drive way".
In short, packages are not GPS tracked, just checked off at waypoints,
I have also tracked trucks and shipping containers (outdoor stuff).
Where a 'phone network is available, we periodically get a GPS fix & send it by SMS (which is generally cheaper than using TCP (although Singapore is a special case, with almost complete free wifi coverage)).
Out of network range, we use cheap (US $500) low data rate satellite modems, such as those from SkyWave.
Note that we pros tend to prefer GPS for accuracy, but you can also use Google Maps, which will traingulate on cell towers, with less accuracy.
Indoors, it gets really tricky & you can choose between having some sort of scanner in doorways, or or having your device traingulate on the signal strength of wifi routers, etc
But, I am digressing here, so feel free to ask further quesitons, if intersted, for more detailed answers.