The following information is from a DMA dissertation out of Louisiana State University in 2005 titled "Dragos Tanasescu's 'Treatise of Pianistic Technique'" by Lucian Zidaru:
"Tanasescu’s 'Treatise of Pianistic Technique' has been published only once, in 1985, in Romania and only in the Romanian language. The publishing company that published Tanasescu’s work in 1985 did not have a copyright. Romania at that time, being a communist country, did not have copyright laws. The publishing company belonged to Ciprian Porumbescu Conservatory. It served only the internal needs of Ciprian Porumbescu Conservatory’s professors and students." (p. 110)
The full text of the dissertation is available from LSU's website here
. Perhaps the dissertation itself will tell you what you want to know.
In any case, searching library catalogs or used book services under the English title is unlikely to locate a copy if the work was only published in Romanian and little distributed outside Romania.
(Added note: A little googling turns up the fact that Lucian Zidaru, the author of the referenced dissertation, is now on the faculty of Dillard University
in New Orleans. He apparently did his undergraduate music studies in Romania, so perhaps he has a personal copy of Tanasescu's method that he used for his doctoral work. I suspect it would be easy to contact him via email through his university with questions.)