Would the laser have any negative effect on the tissue surrounding titanium plates?

If you have metal implants in the electrical pathway ( between the electrode and the neutral pad) you should  avoid using RF. Metal has the capacity to conduct energy and/or become warm. Titanium has low conductivity, however, it does get warm. And you do not have a way of measuring or calculating the temperature the Titanium Plate will reach, and therefore, you are risking injury in the tissue surrounding it.
I do not recommend you use Tempsure around your eyes or forehead. However, you could use it in other parts of your body. Just make sure the plates are not on the energy path.

TempSure  heats the skin via radio frequency. I am not aware that it effects titanium plates, but that is a good technical question for your Cynosure representative. I think they answer those types of questions honestly. But, honestly I think they over sell the esthetic benefits of  TempSure . It has almost no effect on people over 50 and is minimally effective for younger people. 

Because Titanium is not really affected by heat and electricity, it is unlikely to have an adverse affect. That being said, always be upfront with your doctor and coordinate the treatment accordingly.  Exercise caution above all and communicate.  If you do this treatment and feel any discomfort, make sure your doctor knows.  You may want to leave this area alone or only treat for a short amount of time.  Discuss this with your doctor.