Interferes with CBL-mediated down-regulation and degradation of receptor-type tyrosine kinases. Promotes accumulation of activated target receptors, such as T-cell receptors and EGFR, on the cell surface. Exhibits tyrosine phosphatase activity toward several substrates including EGFR, FAK, SYK, and ZAP70. Down-regulates proteins that are dually modified by both protein tyrosine phosphorylation and ubiquitination. {ECO:0000269|PubMed:15159412, ECO:0000269|PubMed:17880946}. This is the function of UBASH3B (ubiquitin associated and SH3 domain containing B, ENSG00000154127).