Yep. Mechanized Infantry are just an abstraction of Infantry + Small Support Vehicle. One of many necessary evils for running infantry at scale under TW rules.
In A Time of War and MechWarrior: Destiny, you would represent Mechanized Infantry as a Small Support Vehicle + Infantry by default, with Small Support Vehicles having slightly different rules for armor and such that makes playing them a bit more in-depth, not to mention the drastic improvement to infantry mechanics.