Well, no answers because there are very FEW people on that way...
I walked it last year.
I met people in Irun where I started - most of them were to take the Costal road...
I met one Italian woman after the first day in Hernani.
And one German man just after Vitoria...
All the rest of the camino, I was on my own (and I started end of June!!!)
I did not reply as well because I took alternatives routes...
From Irun to Zegama on a Mountain way (ancient "transhumance" routes - at least what my German guide book said...)
And after la Puebla de Arganzon, I went via Miranda do Ebro directly westwards to Burgos.
So I "missed" Haro...
It was a different route than the "traditionnal" Tunnel route.
Really lonely, quite adventurous (as to way marking, food supplies, sleeping possibilities...) but as on the other caminos, I have to admit : "Santiago" takes care of you...
Nevertheless, Sabine, if you want some information, don't hesitate.
PS it took me 12 days, but mountain etapes had to be either short (+-15km) or very long (30km) and the alternative via Mirando to Burgos is a little longer - but to arrive farer westwards