We study the existence of fully-heavy hidden-flavor $bcbar{b}bar{c}$ tetraquark states with various $J^{PC}=0^{pm+}, 0^{--},1^{pmpm}, 2^{++}$, by using the moment QCD sum rule method augmented by fundamental inequalities. Using the moment sum rule analyses, our calculation shows that the masses for the S-wave positive parity $bcbar{b}bar{c}$ tetraquark states are about $12.2-12.4$ GeV in both $[mathbf{bar{3}_c}]_{bc}otimes[mathbf{3_c}]_{bar{b}bar{c}}$ and $[mathbf{6_c}]_{bc}otimes[mathbf{bar{6}_c}]_{bar{b}bar{c}}$ color configuration channels. Except for two $0^{++}$ states, such results are below the thresholds $T_{eta_ceta_b}/T_{Upsilonpsi}$ and $T_{B_cB_c}$, implying that these S-wave positive parity $bcbar{b}bar{c}$ tetraquark states are probably stable against the strong interaction. For the P-wave negative parity $bcbar{b}bar{c}$ tetraquarks, their masses in the $[mathbf{bar{3}_c}]_{bc}otimes[mathbf{3_c}]_{bar{b}bar{c}}$ channel are around $12.9-13.2$ GeV, while a bit higher in the $[mathbf{6_c}]_{bc}otimes[mathbf{bar{6}_c}]_{bar{b}bar{c}}$ channel. They can decay into the $cbar c+bbar b$ and $cbar b+bbar c$ final states via the spontaneous dissociation mechanism, including the $J/psiUpsilon$, $eta_cUpsilon$, $J/psieta_b$, $B_c^+B_c^-$ channels.