I cant remember seeing any papers on direct binding of ThT to actin or tubulin filaments. But there are reports of proteins that bind to tubulin and actin that can aggregate and bind ThT.

http://147.46.242.194/pub/myunghye_BBRC365(628-35).pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439503/

Short answer to your question is no. ThT binding is not exclusive to amyloid fibrils.

The binding of ThT to fibrils and its mechanism may be best explained on the basis of the protein conformation state (beta sheet) and the fibril characteristics. Its affinity for binding to fibrils with positive charge or at low pH is greatly reduced. With regards to binding to non-fibrillar protein conformations, ThT binding to proteins such as human serum albumin and acetylcholine esterase have been reported, so confirmation of fibrillar structure by other methods may be necessary. Not sure if it binds to the proteins in question.

Some years ago I read this paper on the mechanisms of ThT binding.

Journal of Structural Biology 149 (2005) 30–37

There is a long discussion of ThT and other fluorescent probes here

https://www.researchgate.net/post/Amyloid_protocols_project

and on the associated project page (Amyloid Biophysical Methods bench)

Th T can binds with fibrils with beta sheet conformations. it is not the exclusive indication that the fibrils are amyloid. For amyloid fibrils it should shows the birefringence under polarize microscope.