Yes, but this says more about the Left," than about the sort of politics that a) lead to good policies, and b) can appeal to the population.
Application of the term 'labor-aristocracy' to the populist right glosses over a lot. Worker-friendly trade policy appeals to all sorts of workers, with those most imperiled by trade -- the "lower skill" (sic) workers in textile, for instance -- often at the bottom of the wage scale. Trade is not a labor-aristocratic trip. On immigration, there are clearly counter-vailing tendencies within labor and within the working class. The most dynamic unions are driven by immigrant-related populations, as you know. Ultimately I would predict optimistically that this fact has to impress their native-born bretheren, with whom many common interests are shared.
When Buchanan talks about sovereignty, it is directly in reference to regulatory matters which are exclusively the province of the left. So he's a hypocrite, but the concerns are not venal, nor are they irrelevant to the working class, nor to the Catholic social teaching.
The problem for the left is that in the hands of the right, the sovereignty issue is conflated with nativism, racism, jingoistic nationalism, and ravings about 'world government,' and for obvious enough reasons. But there remains an important corpus of program and politics being exploited by the right for which the left needs to establish a monopoly franchise.
The same ambivalence goes for the Catholic social movement, as you have noted.
>From what some would dub a 'left-conservative' standpoint,
I would simply urge a sympathetic reassessment of all the
issues where the left differs from working people, whether
of the Catholic social teaching variety, or the neo-isolationist
tendencies. Not because "the people" must be right, but
because they can be.
mbs