Seattle has street plantings of P. fraxinifolia, although there have been some removals as these have became problematic. P. x rehderiana, P. rhoifolia and P. stenoptera are also seen - although the latter is known only in that city from several plantings in the Washington Park Arboretum. Since P. stenoptera produces its leaflets on a strongly winged common stem, I wonder if the tree shown above might instead be another species in the genus.
From the Flora of China, a wingless leaf rachis in combination with slender seedwings should mean P. tonkinensis, but the leaflet shape (blunt, not acuminate, apex) matches P. stenoptera much better, and P. tonkinensis is very rare in cultivation (only fairly recently introduced). According to FOC, "Transitional forms occur where the ranges of two species overlap", so it could be one of those.
Photo of infrutescence (and what can be seen of leaves, in background) of P. tonkinensis on page 678 of Grimshaw/Bayton, New Trees - Recent Introductions to Cultivation (2009, IDS/Kew) and photo linked to in list on this page http://jmvanel.free.fr/hypervert/node69.html look like tree asked about on this thread (when you click to enlarge photo reached via link I have posted here, the leaves can be seen just well enough to tell they are similar if not same). New Trees also says a seedling of P. tonkinensis from Kunming Botanical Institute grew 10 m tall in 9 years at the Raulston Arboretum, and that seedlings of this specimen have been widely distributed. The book also relates that no specimens that fit the bill are known in Britain. One at RBG Edinburgh resembles P. stenoptera. Both it and the Raulston accession came from Kunming. Lingering web site of now closed Piroche Plants wholesale nursery in Pitt Meadows says they had P. stenoptera starting 1992. This company featured seedlings of various trees and shrubs imported from Chinese sources. Perhaps the tree asked about here was one of those received and sold by them as P. stenoptera.
Yep, saw the New Trees detail; I was rather assuming that the 2nd-generation seedlings from the Raulston tree probably wouldn't be old enough to be fruiting themselves yet.