Yeah mentioned a bit already, I'm not entirely sure. Looking at immigrant heavy and lower income areas - Meyrin was at 57% yes; Vernier at 59%; Onex at 60%; Chêne-Bourg at 65%. In Geneva itself Servette was a little over 60% but Paquis was on 69%. So they did pull the canton to the right a little bit, but they always do on these sorts of issues - that didn't stop the canton from being at 76% Yes (compared to 63% nationally) on the anti-LGBT-discrimination law a year and a half ago.
More interesting is that, as mentioned earlier, the rich left bank suburbs had pretty low scores and even the university neighourhood of Plainpalais - normally one of the most left wing voting booths in the country - was "only" 73% Yes. In comparison the equivalent low income, immigrant heavy neighbourhoods of Zürich Kreis 12 and Schlieren were around 68% Yes - so the answer isn't there.
The story really is comparatively tepid support across French Switzerland as a whole - the patterns within Romandie are actually fairly normal. As in, Vaud, Geneva and Neuchâtel voting furthest left; the Valais, the rural Fribourg districts, Jura Bernois and Ajoie all being further right (but with much less rural-urban polarisation than in German Switzerland). The difference is just that the region as a whole voted more relatively conservatively than it normally does. Which contrasts to the normal service in the 99% initiative, so it's not down to turnouts either.
The reason as to why? I'm not sure. There was a particularly hard rejection of the law among the Valais Christian Democrats, plus the influence of the conservative (old Liberal party) element in the PLR that led to some fights within the party. For example the Geneva Young PLR initially rejecting the law before backtracking. But beyond that, it's speculation, and I guess it's just one of those things that pops up when you have different linguistic regions having different debates and different campaigns and not always interacting with each other that much.
The answer might be partially non-political. There is a point at which certain positions, particularly with both broad and deep support, no longer result in lop-sided support in favour, that you might otherwise see based on demographics, in a result closer to 50-50. You'll still see some more lop-sided 'against' due to committed votes against a proposal. But 'Yes' finds a ceiling a little below than what you might expect.
In Ireland, it was 62% Yes overall, but in Dublin, no more than 70-75% in very favourable demographic constituencies. Australia, excluding very LGBT friendly districts, had a similar spread.
