While what you've posted will work in RHEL 6, I see that RH have somewhat quickly deprecated using inittab for running TTYs.
The stuff in /etc/init is from Upstart (I thought you'd be familiar with that coming from Ubuntu) a replacement for sysV initialization (i.e. what used to be in /etc/init.d and /etc/rc.d/rcX.d dirs). And in the case of the files you specify, configures the serial port hardware.
When all else fails RTFM:
The /etc/inittab file is deprecated, and is now used only for setting up the default runlevel
To configure a getty running on a non-default serial console, you must now write an Upstart job instead of editing /etc/inittab. For example...
I suppose it makes sense to start the getty's on a modern machine lower in the stack than the inittab. However for the purpose of providing backup remote admin access, I think it would be far more sensible to start a console on the serial port. i.e. see the stuff about /etc/init/start-ttys.conf