Sorry for the ignorance but i deal alkmost entierly in the 401k world. I have a 501©3 client with a 401a plan and they are contemplating a deferral only 403(B)7 plan. If they make matching contributions or non-elective contributions to the 401a plan, does that make the 403b subject to Title I of ERISA?

No. It's based on what they do with the 403(B) arrangements themselves.

If the matching contributions to the 401(a) plan are based on what employees defer to the 403(B) plan, then this might be a role beyond what is authorized for employers in the regulatory safe harbor for non-ERISA 403(B) plans. If that's your case, I suggest you contact your ERISA attorney. The worst case is for you to treat the 403(B) as a non-ERISA plan and later have it determined that it was subject to ERISA.