Ctrl-Shift-C/V/X are not implemented in bash; it's the terminal emulator program that handles these. So the default terminal emulator of Ubuntu (gnome-terminal I assume, but ICBW) knows about a “system” clipboard and copies stuff to it and on paste feeds bash with the copied data. If you press Ctrl-Alt-F1 (and F2, F3, depends on your distribution's defaults) you can login and in your login shell, which I understand is bash, Ctrl-Shift-C/V/X have no difference to shiftless Ctrl-C/V/X.

When you press CTRL and a letter or symbol at the terminal, shift doesn't do anything (unless it's required for the symbol, as in CTRL-@). The code that gets sent is the same either way. Emacs users have to be wary when setting custom keybindings because GUI Emacs can see the difference but terminal Emacs can't.

Likewise, ALT just sends ESC assuming you're using the standard US keymap.