bash now requires the "-l" and "-c" to be specified explicitly in the cron job which I swear it did not before but that's the same way it's always worked according to them, and well, it's par for the course because there's always going to be a proprietary "closed shop" somewhere working overtime to cripple my business and earn heavy consultancy fees at my expense by wrecking anything technical they can get their hands on behind the scenes.
Depends on the distro (and maybe on user choice). @justinacolmena said they're running CentOS, here it's indeed a symlink to bash though bash runs in a special POSIX mode when invoked through /bin/sh.
Other distros may use different shells, for example Debian/Ubuntu use dash.