In a television discussion between the former Home Secretary, Jacqui Smith, and the presenter Andrew Marr, both used the pronunciation ˈspaʊzɪz for spouses (pl).
I think (though without any hard evidence) that most people pronounce this word with a voiceless sibilant at the end of the stem, ˈspaʊsɪz. (There is also a jocular plural spice spaɪs, like mouse—mice.)
There are two possible explanations for the voiced sibilant pronunciation: (i) the speakers in question say spaʊz for the singular noun; or (ii) they say spaʊs in the singular, but switch voicing for the plural.
Many dictionaries do record spaʊz as a possibility for the singular noun, although EPD/CPD is not among them. I would be pretty confident in saying that in BrE at least it is very much a minority preference.
So explanation (ii) seems to be more likely. The explanation for a switch in voicing would obviously be the analogy with house haʊs — houses ˈhaʊzɪz (which is pretty general among native speakers, though Scots seem often to have the regularized ˈhaʊsɪz).
Although house is the only stem in s which switches voicing for the plural in this way, the “minor rule” involved applies to a fair number of stems in voiceless fricatives at other places: f-v in leaf—leaves, wife—wives, sheaf—sheaves etc, θ-ð in oath—oaths, truth—truths, mouth–mouths, and less reliably in path—paths, bath—baths; moth—moths in AmE but not BrE. There are no instances of ʃ-ʒ alternation.
The labiodental cases are supported by the spelling, f-v. But this naturally does not apply to those spelt th or s.
The alternation is better supported in noun-verb pairs, where the noun has s but the verb z: use, abuse, advice/advise, loss/lose, spouse/espouse as well as house. (But only Germans think that leasing has z.)
It would be unusual for an exceptional pattern (minor rule) to be extended to new vocabulary items. That is why ˈspaʊzɪz seems worthy of comment.