Buster 11,
I have researched the activities of the Yak-25RV Mandrake and the Myasishchev M-17 Stratosphera (
MYSTIC-A/B) for many years but, without access to the USSR/Russian archives, information is either limited or subject to exaggeration by those with a vested interest. However, there is no evidence whatsoever that either aircraft overflew either West Germany or any other NATO country. In reality both aircraft had insufficient high level performance and had they ventured over the border they would have been vulnerable to interception by either aircraft or missile; both aircraft had fairly short service lives, particularly when compared to the U-2.
Heimdall
The Spyflight Website Yakovlev Yak-25RV.
Myasishchev M-17 Stratosphera (Mystic-A/B)