Yes - according to this link.
Do a ctrl+f search for "arabic", you will see it.
It is called "Star Translate" and it says it is free :).
I'm not so sure if it is exactly a TTS or just a translator, but the website is titled "Speech Enabled Applications", so it's probably worth a try.
Also, according to this link, SVOX offers an Arabic TTS as well.
Let me know if any of these work :).
