Blooming at this time of year, my first thought was Leptodermis, but leptodermis flowers have five petals, and with more narrow leaves. It's definitely a syringa, and there are some that bloom in the fall, but not Palibin. Lilacs that bloom only in the spring, like Palibin, have flower buds that are produced in the summer and remain through winter to bloom the following spring. It is extremely doubtful there could already be enough cold for a long enough period to trigger bloom of Palibin, even in a very weird fall in iceland, I suspect.
I think it is one the the lilac cultivars that can normally bloom in the fall, like Josee.
As for the variegated leaves, it could be a virus, but more likely it is a trait of the cultivar.