Will the Networking Fundamentals and Security Fundamentals certifications prepare you for the A+ and Security+ certification exams?
Exam Path Question
I would love to say that these directly prepare you for the CompTIA exams you mention but they are not directly related in a exam path.
The MTA, Microsoft Technology Associate, is to give a "taste" of the technologies that an ITProfessional will encounter in a business environment. In itself, they are not so much a "preparation" as much as an "introduction" to different specializations you're likely to find in IT.
Having said that, the concepts covered in the MTAs are helpful since they introduce you to the technologies you're likely to see on IT exams. The familiarity with the terminology and basic functional knowledge of the technology will mean less ramp up time to prepare for other certs.
Let me know if this is unclear and I will try to help.