Guess it depends on how they interpret their customer agreement:
What Are My Rights for Dropped Calls or Interrupted Service?
If you drop a call in your Coverage Area, redial. If it's answered within 5 minutes, call us within 90 days if you're a Postpay customer, or within 45 days if you're a Prepaid customer, and we'll give you a 1minute airtime credit. If you're a Postpay customer and you lose Service in your Coverage Area for more than 24 hours in a row and we're at fault, call us within 180 days and we'll give you a credit for the time lost. Please be aware that these are your only rights for dropped calls or interrupted Service.
The italic part is relevant, the bold part perhaps more so. A natural disaster is certainly not their fault, though a failure to provision backup generators and such may well be.
If I was to hazard a guess, they'll quietly give refunds to those who ask for them, but not publicly advertise the availability of said refunds.