Originally Posted by
DownUnderFlyer
No you don't. BMED used to be a BA franchise and is now part of Star Alliance via BMI. Luckily comair has renewed their BA franchise for another 11 years otherwise your trip to MRU wouldn't work anymore.
There are AY operated flights between St Petersburg and Helsinki every day plus some codeshare, so you should be fine.
BTW the flight to SSG is not on the oneworld map yet, so good find. Hopefully it will be updated soon.
It appears to be on the oneworld interactive map
here. Type in MAD and it shows up.