Its even possible to solder plain aluminum with ordinary SnPb or Pb-free solder without special 'aluminum' flux. A freshly cleaned aluminum surface is solderable, but one with a layer of aluminium oxide is not. Unfortunately the aluminum oxide layer forms extremely rapidly in air at elevated temperatures, and in minutes at room temperature, so you have to exclude air from the work - either with an oil stable at soldering temperatures or with copious quantities of a good gel flux.
What does this mean for soldering CCA wire?
As Tooki mentioned you have to be fast getting the wire tinned. If heavily tinned, you can then reflow it to form a joint with a previously heavily tinned terminal. Use plenty of flux. However that copper layer dissolves in the solder very quickly, so if the solder film gets scraped off while reflowing it, the exposed aluminium will oxidise and will be difficult or impossible to re-tin.
Then there's the issue of stranded wire embrittlement at the surface of the joint. Aluminum is less ductile than copper, its copper coating will have been scavenged by the solder, necking each strand down and leaving a thin ring of exposed aluminum, and aluminum in contact with copper is extremely vulnerable to corrosion, so unless you get *all* the flux residue cleaned off and the joint coated with lacquer to exclude air and moisture, you are setting yourself up for failure if you solder stranded CCA.