There are several command line options available for Firefox (all listed here: https://wiki.mozilla.org/Firefox/CommandLineOptions), however there seems to be no option to open an URL in a specific container.
A possible workaround might be to set "always open this site in...", however this does not work if one needs to use the same website with different containers/accounts.
One possible idea for the option could be to add an option --container [NAME], such as --container "Work", or --container [No.]