Do plasma B cells express the BCR or only produce soluble antibodies?
B cells can secrete antibody before they are terminally differentiated into plasma cells, so there is a phase during which both membrane-bound and secretory antibodies can be produced by the same cell:


  When a naïve or memory B cell is activated by antigen (with the aid of a helper T cell), it proliferates and differentiates into an antibody-secreting effector cell. Such cells make and secrete large amounts of soluble (rather than membrane-bound) antibody, which has the same unique antigen-binding site as the cell-surface antibody that served earlier as the antigen receptor (Figure 24-17). Effector B cells can begin secreting antibody while they are still small lymphocytes, but the end stage of their maturation pathway is a large plasma cell 


--Molecular Biology of the Cell. 4th edition. 

Plasma cells, generally speaking, have little or no surface immunoglobulin, but it's been claimed that some subsets of plasma cells do have surface Ig:


  Surprisingly, although IgG PCs downregulated surface IgG expression, IgA and IgM PCs expressed their respective isotype both intracellularly and on the plasma membrane (Figure 1A, lower panel). Importantly, concordant Ig’s were also detected on the plasma membrane of IgA and IgM, but not IgG, PCs isolated from BM or colon LP indicating that this property is a characteristic of PCs present in their physiological niches 


--A functional BCR in human IgA and IgM plasma cells