Part 61.157(f)
 

(f)Proficiency and competency checks conducted under part 121, part 135, or subpart K of part 91.

(1) Successful completion of any of the following checks satisfies the flight proficiency requirements of this section for the issuance of an airline transport pilot certificate and/or the appropriate aircraft rating:

(i) A proficiency check under § 121.441 of this chapter.

(ii) Both a competency check under § 135.293(a)(2) and § 135.293(b) of this chapter and pilot-in-command instrument proficiency check under § 135.297 of this chapter.

(iii) Both a competency check under § 91.1065 of this chapter and a pilot-in-command instrument proficiency check under § 91.1069 of this chapter.

(2) The checks specified in paragraph (f)(1) of this section must be conducted by one of the following:

(i) An FAA Aviation Safety Inspector.

(ii) An Aircrew Program Designee who is authorized to perform proficiency and/or competency checks for the air carrier whose approved training program has been satisfactorily completed by the pilot applicant.

(iii) A Training Center Evaluator with appropriate certification authority who is also authorized to perform the portions of the competency and/or proficiency checks required by paragraph (f)(1) of this section for the air carrier whose approved training program has been satisfactorily completed by the pilot applicant.

Could somebody explain this reg in simpler words. Would this mean that by having a 293 or 297 check I would not have to take the practical test? Or that I would not need a sign off from a CFI?

It means a 135 or 121 checkride can be your practical test if the company check airman is a designee. There's no requirement for a CFI sign off for an ATP.

So any company FAA check airman could in theory give me the ATP checkride? By having my 135.293 & .297 checks done?

I currently work for a operator in a remote pacific island and could take some months for the FAA to visit us.

You already posted the answer when you quoted the regulation:

(2) The checks specified in paragraph (f)(1) of this section must be conducted by one of the following:

(i) An FAA Aviation Safety Inspector.

(ii) An Aircrew Program Designee who is authorized to perform proficiency and/or competency checks for the air carrier whose approved training program has been satisfactorily completed by the pilot applicant.

(iii) A Training Center Evaluator with appropriate certification authority who is also authorized to perform the portions of the competency and/or proficiency checks required by paragraph (f)(1) of this section for the air carrier whose approved training program has been satisfactorily completed by the pilot applicant.

No, not any company check airman. A company check airman who is also an APD. Does your company have check airman that issue type ratings? They normally can issue the type and the ATP at the same time. A check airman who just does the company 6 month rides may or may not be an APD.

The usual path for ATP + Type Rating + 135.293/.297 is via a Part 142 TCE / Contract Check Pilot at FSI, CAE etc...

The purpose of this rule is for a certificate holder that wants to be able to issue ATPs concurrent with checks. This is so they can take someone with a decent amount of hours and experience, take them through the ground and flight training, and test and issue and ATP right before putting them on the line. This usually has to reside within the training program. Many airlines do this. No, it cannot be done by a check airman (already answered).