I had similar boards from Motorola equipment, and I found that the traces were Pt (at least in my case). I haven't processed the IC's yet, so I don't have any yield data. I believe the MLCC's are also non-magnetic type.
I soaked mine in Hydrochloric long enough to remove the solder and for most of the SMD's to fall off.... I had to pick off the rest of the SMD's to have clean enough boards to process. I had to AR them for a while until the solder mask slips off, exposing the rest of the traces.
I doubt the sub-straight is Be, but I wouldn't take any chances.
So don't grind them up. Again.... I don't know if yours is Pt/Pd or not, so I would just process one of each and do a stannous test.
In case you don't know... PGM's, when they are in solution are very toxic and protections need to be in place.
If you decide to test them, let us know the results.