The Builders Lien Act provides no express instructions as to who should be defendants in a lien action:
Unlike, for instance, the Saskatchewan Builders' Lien Act, S.S. 1984-85-86, c. B-7.1, considered by the Saskatchewan Court of Appeal in Wellington Insurance Co. v. Saskferco Products Inc. 1999 CanLII 12236 (SK CA), (1999), 170 D.L.R. (4th) 625,  7 W.W.R. 473, which contained an express provision as to who shall be parties to a lien action, the British Columbia statute contains no such procedural instructions.
(Paramount Drilling and Blasting Ltd. v. North Pacific Roadbuilders Ltd., 2005 BCCA 378 at para. 26).
The owner of the land should likely be named as a party to the lien action even if money has been paid into court under s. 24 as substitute security in place of the land:
The owners of the property remain necessary parties to any action to enforce the lien, as the action is enforcing a claim in rem against their property. Under s. 24 they remain possibly liable for amounts not covered by the security, even though the statutory scheme of the current Act overall will often make their participation in the litigation ‘nominal or notional’ where the security is posted by another party. While in such situations it may be undesirable to force the owners to participate in an action which is almost certain to result in no liability on their part, the changes manifest in the current version of the Act do not render the owners unnecessary parties.
(Paramount Drilling and Blasting Ltd. v. North Pacific Roadbuilders Ltd., 2005 BCCA 378 at para. 25.
However, other cases have commented that the owner need not be named when security has been posted:
There was no need to keep the School District in the action because the amount of the lien and costs had been secured by the lien bond.
(0690860 Manitoba Ltd. v. Country West Construction Ltd., 2009 BCCA 535 at para. 11).
Depending on the facts in play in each particular case, the following parties may be named as defendants to the lien action
(a) The party contractually indebted to the claimant.
(b) The owner(s) whose interest the lien claimant wants to attach.
(c) The lessees, if any, especially if the owner has filed a notice of interest.
(d) The mortgagee, especially if priority is being claimed over funds advanced under the mortgage.
(e) If there is a registered agreement for sale, the purchaser under the agreement for sale (especially if the purchaser is the party that commissioned the work).
(f) The party who posted security for the claim of lien under s. 24 of the Builders Lien Act.
(g) A party the lien holder claims priority over (e.g judgement creditor with registered judgement).