Part of the challenge here is that flying transatlantic ex the Canaries will get traffic originating or ending at the Canaries. All flights to the Canary Island are usually pricy, as it attracts mostly holiday traffic and I'd agree with earlier comments, the market is small, I.e. the population of the Canary Islands, i.e. residents. Hence limited opportunity for interlining passengers via the Canaries to US and South America.
Any carrier looking at this market will face opposition from not just Iberia, but Air Europa who feed traffic via Madrid to the mentioned destinations.
My money would be on this being a non starter...
It is on the other hand amazing the sheer level of traffic ex MAD to Latin and South America, yes there are huge links culturally, but the volume of traffic is quite impressive.