Inmarsat has a country code of 00870 or +870
So if your Iridium can call for example a German number by prefacing it with 0049 you should be able to call an Inmarsat number in the same way.
https://www.inmarsat.com/support/carrier/ says:
Calls from the terrestrial telephone network (PSTN) to an Inmarsat network are made using the Inmarsat +870 international dialling code.
https://www.iridium.com/support/making-calls/ says:
Example 4 – Originating a call from an Iridium satellite phone (does not matter where the satellite phone is located) to a landline phone located in another country.
From the satellite phone, dial: 00 CC XXXXXX
00, for all outbound calls from satellite phone/CC, country code/XXXXXX, actual number.
So i don't see why you shouldn't reach the Canaries under the phone number 00 870 424 201 using an Iridium sat phone or really just any other phone.
(But it might be a special number only reachable from within the Inmarsat network, which would be kinda stupid)