EDIT: As Martin points out, Bing can still index the site with SSL links in SERPS even though it errors on SNI -- the error occurs before the following results. The following is arbirtary for the question.
Bing does support SNI [Edit: as in it can still successfully index SSL links]. Im looking at a multidomain multiSSL via SNI setup right now, clicking the SERP results drop me https. Also, looking at 30 minute sessions, the last pages it crawled are all https-mode.
Based on past esperiences with sharedSSL and TLD derivitaves -- if a certificate is invalid, for another domain, or whatever, there is about a 99% chance it wont index. If it does index, most likely it will flag a warning in SERP or it wont stick. We have a site that has invalid SSL and malconfigured subdomain SSL (since its SNI server) and even though the https there is accessable, and various links point https, it has never been indexed with its non-accurate [invalid] SSLmode.
Hope i understood what you were asking!