Can the same lawyer act for me and my lender in New Brunswick?

This answer covers the law of New Brunswick.

Often yes, but it depends on your lender's instructions and on the professional rules your lawyer follows, so ask before you sign anything. Electronic deeds and mortgages can only be submitted by 'subscribers', meaning Law Society of New Brunswick members authorized to practise law who have an agreement with Service New Brunswick, apart from stated exceptions such as a registered owner submitting an instrument personally on paper.

Whether your purchase needs a lawyer at all also depends on your lender's requirements, so confirm this with a lawyer. The mortgage is registered in prescribed form and is deemed to contain the prescribed covenants and conditions. Still, you and your lender have different interests: you want workable terms, while the lender wants its security properly registered. Ask the lawyer plainly who they act for, whether the lender is also a client, and what happens if your interests conflict.

Later, a registered mortgage can be discharged by registering a discharge of mortgage in prescribed form. Whether one lawyer can properly act for both sides, and what duties they owe each of you, depends on the facts and the Law Society's rules, so ask for the answer in writing and get a second opinion if unsure.