Nope. I wouldn't be able to shield the 900 Sectors on that tower so shielding the Nano wouldn't have proven out what I needed to do.
I've seen 900 Mhz Filters available. Never Tried one. Maybe choking each unit to opposite sides of the band would help ? Since both are in plastic cases they are gonna bleed like mad before the chokes too so shielding both units is probably going to be needed as well.