MEO recently switched us to fibre optic. Because our landline phone would now be routed by fibre rather than copper cable, I asked what would happen in the event of a power cut. We were told the landline would not function as it passes through the router.
OK, that made me think about the cell phone service. So I checked, and this may function for a short period if the local tower has a back up power source. It will not work if it does not have back up.
Worst outcome you could be stranded with no access to emergency services. I spoke to Civil Protection about this and they were aware of the potential problem. His only suggestion was, if there was a medical emergency or fire, to send a neighbour to raise the alarm at the local GNR or Bombeiros. Also, possibly invest in a CB radio, as he said that Bombeiros and possibly GNR have these.
In view of the current threats of extended power outages, please be aware and make contingency plans.