Hi there
Like anything of a similar nature, the car alarm needs to be fitted correctly and properly in order not to set off false alarms.
These GSM based 'alerting' systems are good, but I'd question their performance if your car is sealed up in a steel container in amongst other steel containers in a storage yard/facility. I'd have doubt they'll pickup a signal!
Is there any reason your putting the car into containerised storage? and for how long? reason I ask is that you'll need to do some basic long term car preparation before doing so. Things like sealants, gaskets, battery & electricals, seals etc all need to be looked at prior so that when you bring the car out of storage, you've the best chance all will be intact and able to function nicely without you firing the engine and making some expensive to fix sounds!
Related to the above, your battery will probably go flat if you leave it connected, so the alarm would be useless anyway. If you disconnect the battery, you'll incur extra charges I'm sure if you need a power supply to keep the alarm working, and that's if theres a signal able to be used!
Cheers, DtM! West London & Slough UK!