Names tend to be the worst contenders for following general rules. So what speech recognition and tetx-to-speech systems potentially do is have a big database of exceptions. For some applications, e.g. automated telephone directory services, knowing the pronunciation even of fairly unusual surnames is important. (I did some work for a speech technology company where I and other linguists did precisely that: take a huge list of names and create a database of phonetic transcriptions. Needless to say, it's quite painstaking work.)
On the other hand, a general TTS system may either not include such a large database of names and/or not always be able to predict accurately when it needs to use that database. For most general TTS applications, the vast majority of words do not consist of unusual names, so including such a large database of exceptions for the sake of unusual names could actually increase the error rate overall for an average sentence.
Your best bet is: use the best-quality TTS system you can find (NOT the ones built into Windows which are completely dreadful) and type a phrase which obviously hints at the name in question actually being a name (e.g. "Hello, Mr _").Maybe compare with another high-quality system. And still take with a pinch of salt.